UC-NRLF 
 
 Sflfl 
 
THE MICROSCOPICAL 
 
 EXAMINATION OF POTABLE 
 
 WATER. 
 
 GEO. W. RAFTER, 
 
 MEMBER OF THE ROCHESTER ACADEMY or SCIENCE. 
 
 SECOJSTID EIDITIOIST. 
 
 NEW YOEK : 
 
 D. VAN NOSTRAND COMPANY, PUBLISHERS, 
 
 23 MURRAY AND 27 WAEEEN STREETS. 
 
 1900. 
 
COPYRIGHT, 1892, 
 BY D. VAN NOSTRAND Co. 
 
 C. J. PETERS & SON, 
 TYPE-SETTERS AND ELECTROTYPE 
 145 HIGH ST., BOSTON. 
 
PREFACE. 
 
 THE publishers of the SCIENCE SERIES having 
 asked the writer to prepare a monograph on the 
 Microscopical Examination of Potable Water, I 
 will endeavor to comply; though that a civil engi- 
 neer should be expected to prepare anything of 
 value on a subject which has engaged the attention 
 of the most eminent chemists and biologists is 
 something of a surprise. Possibly, however, the 
 fact that studies in this direction have occupied 
 my leisure hours for a number of years, and have 
 led to the production of a number of more or less 
 useful papers thereon, may be to some extent an 
 explanation; but it is sincerely hoped that the 
 expectations of neither publishers nor readers will 
 be raised too high. 
 
 This little book has, it is believed, one merit 
 frequently absent in formal works of more preten- 
 sion. It may be taken as fairly representing the 
 state of the art, of which it professes to treat, at 
 the date of issue, namely, at the beginning of the 
 year 1892; that this is a real merit will be appre- 
 ciated by every serious-minded student who has 
 3 
 
had occasion to travel in new roads. To all such 
 who may be interested in the advancement of pub- 
 lic sanitation this monograph is presented, albeit 
 somewhat hesitatingly, in the hope that it may 
 be of essential use in actual work. 
 
 The perfected method of making the quantita- 
 tive enumeration of the microscopical organisms 
 in potable water, which is here described, is the 
 joint work of Prof. William T. Sedgwick and my- 
 self, though both Mr. A. L. Kean and Desmond 
 FitzGerald, C. E., have contributed useful ideas. 
 To Professor Sedgwick must, however, be assigned 
 the credit of working out a really practical method 
 of making these examinations, and to him must 
 be assigned the honor of giving the method a 
 name. The author took the method, as will be 
 shown in the body of the volume, after Professor 
 Sedgwick had put it on a working basis, and added 
 certain refinements of technique. Professor 
 Sedg\Vick has deemed these refinements of suffi- 
 cient value to justify coupling the author's name 
 with his own, and has accordingly described it in 
 the Massachusetts Health Reports as the Sedg- 
 wick- Rafter method. This I acquiesce in, though 
 the statement may be made, that a complete bal- 
 ancing on my part of the account between the 
 biologists of the Massachusetts State Board of 
 Health and myself, would show on the whole 
 transaction a considerable amount still to the 
 credit of that Board. 
 
 In preparing this monograph. I have assumed 
 
that the reader possesses a fairly complete knowl- 
 edge of the optical part of the microscope and of 
 micrometric measurements. On these heads, 
 therefore, only such information is given as is 
 necessary to elucidate the special work in hand. 
 In the same way the technique of collecting, pre- 
 serving, and mounting, as treated in Part I., have 
 been only briefly given. The full detail leads too 
 far away from the special subject. Those not 
 possessing the necessary preliminary information, 
 and still wishing to fit themselves for an intelligent 
 use of the method, may find abundant references 
 to standard literature of the microscope, either in 
 the explanatory foot-notes or at the end of the 
 volume. 
 
 In the same way a knowledge of the funda- 
 mental ideas in relation to modern water analysis 
 is assumed on the part of the reader. Those who 
 do not fully possess such knowledge can hardly do 
 better than to consult the recent Special Keports 
 of the Massachusetts State Board of Health. 
 
 G. W. R. 
 ROCHESTER, JST.Y., Dec. 24, 1891. 
 
NOTE. The small figures throughout the text, 
 thus : MacDonald's Water Analysis, 14 refer to 
 the number of the volume cited in the list of 
 literature following Part II. 
 
MICROSCOPICAL EXAMINATIONS, 
 
 PART I. QUALITATIVE. 
 
 How to Study the Biology of a Water 
 Supply. 
 
 OTHER things being equal, there is in 
 every community having a public water 
 supply, a relation between the degree of 
 purity of such supply and the public 
 health. Indeed, it may be broadly stated, 
 that in a community with a water supply 
 of a high standard of purity, there will exist 
 a lower death-rate than if the standard of 
 purity be materially lower. 
 
 No argument is necessary, then, to estab- 
 lish the proposition, that information rela- 
 tive to the biology of a public water supply 
 is of vast importance, both to individuals 
 and communities; and a study having for 
 its object the solution of biological prob- 
 lems may be safely counted as worthy of 
 intelligent effort. 
 
 7 
 
WORKING-TOOLS. 
 
 For the general study of the biology of 
 a water supply certain handy tools are req- 
 uisite. 
 
 These are the compound microscope, 
 fitted with about the following list of ob- 
 jectives : one-inch, one-half inch, or four- 
 tenths, one-fourth, and one-eighth. The 
 one-half and the one-fourth inch are the 
 most useful. A one-half inch Gundlach, 
 of 50 angular aperture, and a one-fourth 
 inch Bausch & Lomb professional, of 110 
 ^angular aperture, have been found satisfac- 
 tory. For this work the moderate-angled 
 objectives are preferred to those of wider 
 angle. They have better working distance 
 than the wide-angled lenses of recent make. 
 The one-inch, one-fifth inch, and one-eighth 
 inch are sometimes used, but the use of 
 these latter is infrequent compared with the 
 two above mentioned ; and it may be said, in 
 passing, that a very complete study of the 
 biology of a water supply can be made with 
 only two objectives; namely, the one-half 
 inch and the one-fourth. In studying sup- 
 
plies containing many of the larger forms, 
 such as Hydra, Cyclops, Daphnia, Diopta- 
 mus, etc., either a two-inch, or one and one- 
 half-inch would, however, be very conven- 
 ient. 
 
 While thus somewhat radical in express- 
 ing a preference for moderate-angled object- 
 ives for ordinary work, it is but fair to 
 say that for the highest class of biological 
 work wide-angled objectives are nearly 
 indispensable. For any immersion object- 
 ive above one-sixth inch focal distance, one 
 should purchase those of large angular aper- 
 ture. There is, however, in all such object- 
 ives, a considerable sacrifice of working 
 distance to aperture, so that the specific use 
 to which an objective is to be put must to a 
 great extent determine what to purchase. 
 Of one thing we may be certain, that the 
 very wide-angled immersion lenses require 
 a perfection of movement in the micro- 
 scope stand, and a delicacy of manipulation, 
 which add considerably to the amount of 
 time required to complete an examination ; * 
 
 * For very high-power objectives, cover glasses, even of 
 t'.:c thinest glass, are too thick, and ordinary talc split into 
 
10 
 
 so that for the working microscopist to 
 whom time is of value, the question of just 
 what shall be the limit is an important 
 one. 
 
 Of eye-pieces one is indispensable, and 
 two or more are desirable. Where only 
 two are purchased, they should be one of 
 an inch, and one of an inch and a half focal 
 distance. The Huyghenian eye-piece gives 
 somewhat clearer definition than the peri- 
 scopic, but the periscopic has the advan- 
 tage of doubling the field. A fairly 
 complete battery would consist of a one- 
 inch periscopic, in addition to the two 
 Huyghenian eye-pieces above suggested. 
 
 LIFE-CAGES AND CULTURE-CELLS. 
 
 The catalogues are filled with life-cages, 
 growing and culture cells of divers and 
 various sorts, and the beginner in biology 
 is likely to conclude that considerable ex- 
 thin laminae may be used. W. Saville Kent, in his " Manual 
 of the Infusoria," speaks of using laminae of such extreme 
 tenuity that they may be blown away with the lightest 
 touch. With such films Kent says the investigation of 
 the infusoria, with 1-16, 1-25, or even 1-50 inch objectives, 
 becomes a comparatively easy task. 
 
11 
 
 penditure is necessary for apparatus of 
 this sort. The author's experience, after 
 trial of the various life-slides and life-cages, 
 is that for ordinary examination^ a plain 
 slide, with a ring of cement forming a 
 shallow cell, covered with a cover glass, is, 
 on the whole, preferable. Holman's siphon- 
 slide and Holman's siphon life-cage are of 
 use where it is desired to observe the same 
 object continuously for several days. Their 
 expense, however, is considerable, and 
 fairly satisfactory results may be gained 
 with the following device, which has the 
 merit of costing almost nothing. A plain 
 glass slip is taken, and to one side of it two 
 three, four, or more thicknesses of chemi- 
 cal filter paper are pasted, the number 
 of thicknesses depending upon the depth 
 of cell required. The cell is made by 
 cutting out the centre, either round or 
 square, according to the taste or fancy of 
 the operator. In this cell is deposited the 
 organism which it is desired to study. 
 The placing of a cover glass, and the secur- 
 ing of it with a little cement, completes 
 the operation so far as the construction of 
 
12 
 
 the growing-cell is concerned. The cell is 
 placed upon the stage of the microscope, 
 and supplied with water by a rubber tube, 
 acting as a siphon, from a jar standing on 
 a shelf above the stage. The supply of 
 water is controlled by a brass cock placed 
 at the lower end of the rubber siphon tube, 
 set so as to allow water to drop very slowly 
 upon the paper composing the cell, just 
 outside the edge of the cover glass. 
 
 In preparing such a cell, care should be 
 taken to cement the several layers of the 
 paper together at the inner edges, in order 
 to prevent the more minute objects from 
 passing in between the layers. In using 
 it, the slide should be dipped in water, 
 thoroughly wetting the paper before filling 
 the cell, and the delivery of water from 
 the siphon brought to such a rate as to 
 keep the paper constantly wet, just sup- 
 plying the loss from evaporation. The 
 best results will be obtained by setting the 
 microscope vertically. Filter paper is used 
 in its construction, in order to insure that 
 the paper contains nothing likely to kill 
 the object whose life-history it is desired 
 
13 
 
 to study. For deeper cells the best quality 
 of white cotton blotting-paper* may be 
 used, the precaution having been taken 
 to soak it for several days in frequent 
 changes of pure water. For low-power 
 objectives this cell may be constructed of 
 two thin slides, with a layer of blotting- 
 paper between them, the slides held in 
 place by rubber bands at the ends. 
 
 Recklinghausen's growing cell f is stated 
 by Frey to be an efficient device for pre- 
 venting the evaporation of fluids. It 
 consists of a glass ring cemented to an 
 ordinary slide, forming a cell, in which 
 the organism to be examined is placed in 
 a little water. Blotting-paper is folded 
 over the edges of the glass ring, and a tube 
 of thin rubber slipped over this, and con- 
 nected with the objective, being held in 
 place by compression bands. Around the 
 outside of the glass cell several thicknesses 
 of moist blotting-paper are wrapped, and 
 
 * Such a quality of blotting-paper, which is claimed to 
 be entirely free from chemicals, and composed of nothing 
 but pure cotton fibre, may be obtained from the stationers. 
 
 t Frey, on Microscopes and Microscopical Technology, 90 
 p. ,H). 
 
14 
 
 to these additional moisture occasionally 
 added. 
 
 For studying the life-history of very 
 minute organisms, an efficient cell may 
 also be made by inverting a cover glass 
 over a glass cell, with a little water at the 
 bottom, the organism to be studied being 
 contained in a drop of liquid on the under 
 side of the cover glass. 
 
 The moist chamber used by Dallinger 
 and Drysdale in their investigation of the 
 monads is of interest and value,* and illus- 
 trations of it can be found in Kent's "Man- 
 ual of the Infusoria." 
 
 Maddox's growing slide is also worth 
 trial. Carpenter is a convenient reference 
 for a description.! 
 
 Weber's annular cell is an American in- 
 vention, and worth trial.f 
 
 * This cell was originally illustrated in Monthly Micro- 
 scopical Journal for March, 1874. 
 
 t " The Microscope and its Revelations," by Wm. B. 
 Carpenter, sixth edition, p. 145. 8R Originally described 
 by Dr. Maddox in his paper on Cultivation of Fungi, in 
 Monthly Microscopical Journal for 1870, vol. iii. 
 
 $ Carpenter, loc. cit., p. 147. 
 
15 
 
 SUB-STAGE CONDENSER. 
 
 For assisting the illumination, a good 
 sub-stage condenser is at the present day 
 indispensable, and of the several forms the 
 Abbe may be considered the best. It 
 admits of the greatest range of adjustment 
 without loss of time ; and when it is desired 
 to examine an object under all conditions 
 of illumination, this is a matter of con- 
 siderable importance. It is provided with 
 a swinging ring carrying diaphragms of 
 various apertures. The blue glass which 
 accompanies it, for furnishing monochro- 
 matic light when working by lamplight, 
 is also of value.* By its use the objection- 
 able and trying yellow glare of lamplight 
 is entirely obviated; and if one works by 
 lamplight, a considerably larger amount can 
 be done without over-fatiguing the eye than 
 can possibly be accomplished without it. 
 The value of the condenser may be readily 
 shown by a trial of it on one of the test 
 
 * The opticians also furnish a blue-glass mounting for 
 sub-stage, which is adapted to any microscope without the 
 condenser. A blue-glass chimney for the lamp may be 
 made to give substantially the same results. 
 
16 
 
 diatoms ; and probably the most decisive 
 test will be by resolution of the Pleuro- 
 sicjma angulatum, with one-fourth of me- 
 dium angular aperture. Such an objective 
 will only make the resolution "clearly" 
 without the condenser, when the light is 
 somewhat oblique. Moreover, the resolu- 
 tion is not made instantly, but, even with 
 a fairly expert operator, will require a 
 little expenditure of time in manipulation. 
 With the condenser, on the contrary, such 
 an objective will resolve the test instantly, 
 or, at any rate, as nearly so as one can rack 
 the condenser to its proper position in the 
 sub-stage ; and this, too, with the smallest 
 diaphragm in place, so that the resolution 
 is in reality made with nearly central 
 light.* 
 
 The foregoing are the more important 
 tools to be used in a study of the biology 
 of a water supply. For dissections, 
 knives, needles, watch-glasses, tweezers, 
 a dissecting microscope, and other acces- 
 sories, will be required. 
 
 * For hints on the use of the condenser, see " Manipu- 
 lation of the Microscope," 83 by Edward Bausch. 
 
17 
 
 COLLECTING FROM WATER MAINS. 
 
 Whoever undertakes to unravel the 
 problem of the biology of a water supply, 
 will find it necessary to investigate in 
 many directions ; and a few hints on the 
 subject of general collecting are therefore 
 included. 
 
 In the first place, when it is desired to 
 collect samples from the mains of a public 
 water supply without reference to the 
 method of quantitative enumeration, 
 described in Part II., the simple method 
 of fastening a single thickness of fine- 
 cotton cloth over an ordinary cock, and 
 allowing the water to flow freely, will 
 answer every purpose. It is necessary to 
 allow the water to flow full size of open- 
 ing, in order that the various suspended 
 objects may be carried along and brought 
 into the filter ; and two hours of such flow 
 will ordinarily be sufficient. For cleaning 
 the specimens from the filter it should, 
 after removal from the cock, and after 
 turning wrong side out, be either dabbled 
 in a small quantity of water contained in a 
 
18 
 
 deep dish, or washed off with an ordinary 
 laboratory wash bottle. In this way the 
 filterings of a number of hours may be 
 concentrated into an. amount of water not 
 more than enough to fill a medium sized 
 beaker. After standing for a short time, 
 samples may be selected, either from the 
 sediment at the bottom, or from other por- 
 tions of the liquid, depending upon what 
 particular class of organism the operator 
 may be looking for. Further details of 
 this operation, with references to the lit- 
 erature, are given in Part II. 
 
 TRANSPARENT ORGANISMS. 
 
 In the examination, organisms are 
 frequently encountered so nearly trans- 
 parent that the eye fails to discern the 
 structure. In such cases the examination 
 may be materially assisted by the use of 
 some staining reagent which, added to the 
 sample, has the effect of bringing out 
 the hidden structure. For such purpose 
 the various aniline dyes are useful, though 
 probably hsernatoxylin is most frequently 
 applied. For the infusoria, a solution of 
 
iodine, in iodide of potassium, and osmic 
 acid have both been successfully used. 
 They color the structure, leaving the cilia 
 extended. 
 
 The use of first quality objectives, how- 
 ever, by reason of their superior defini- 
 tion, renders the application of staining 
 reagents less necessary than with ordinary 
 objectives. 
 
 COLLECTING FROM STREAMS AND RESER- 
 VOIRS. 
 
 Collections from streams, reservoirs, 
 lakes, or ponds, used as sources or parts 
 of public water supplies, will have to be 
 made by different methods, and the par- 
 ticular one used will depend upon what it 
 is desired to collect. 
 
 For fresh-water algae, the implements 
 needed, in addition to long rubber-boots, 
 are substantially as follows : 
 
 1. A small iron or tin ladle, two 
 inches across, and provided with teeth 
 for one-third of 'the circumference oppo- 
 site the handle. The handle is a hollow 
 ferrule, and serves to attach the ladle to 
 
20 
 
 one's walking-stick. The teeth are bent 
 inward, in order to catch masses of algae 
 beyond arm's-length. 
 
 2. A small sieve is necessary for inter- 
 cepting floating masses of desmids, etc. 
 
 3. A common iron spoon for removing 
 thin layers of mud along the margins 
 where the presence of desmids or diatoms 
 is for any reason suspected. 
 
 4. An iron rake for bringing up sam- 
 ples from the bottom is of value. It 
 should have enough strong cord attached 
 to reach the bottom of the deepest body 
 of water to be examined. 
 
 The foregoing, with a number of bottles, 
 a good pocket magnifier, and a strong 
 jack-knife, will be the principal tools re- 
 quired for collecting the fresh-water algae.* 
 Indeed, the author's own collections have 
 thus far been all made with the help of 
 a few bottles, a walking-stick, a rake, and 
 for objects at a distance on the surface, 
 such means of reaching them as could be 
 readily improvised on the ground. 
 
 * " Collector's Handy-Book," by Jphann Nave. 96 
 
21 
 
 Mr. Wolle's outfit for collecting des- 
 mids consists of four or five tin cans (to- 
 mato or fruit), one within the other for 
 convenience of carriage; ten or a dozen 
 wide-mouthed bottles, and a ring net simi- 
 lar to that described below for collecting 
 the entomostraca.* 
 
 According to the late Dr. Leidy, 
 rhizopods are best collected by the use 
 of a small tin ladle, as above described. 
 Instead of a walking-stick, Dr. Leidy 
 carried on his collecting tours a jointed 
 pole of two or three pieces, each about 
 five feet long. The ladle, or dipper, was 
 used by slowly skimming the edge along 
 the bottom of the water, so as to take up 
 only the most superficial of the ooze, 
 which was then gently raised from the 
 water and transferred to a glass jar.f 
 
 Dr. Leidy states that he was most 
 successful in finding rhizopods in the ooze 
 near the shores of lakes and ponds, possibly 
 due to the fact that the ooze near the 
 
 * " Desmids of United States," by Rev. Francis Wolle,** 
 p. 13. 
 
 t " Fresh-Water Rhizopods of North America," t;7 pp. 
 7 to 13 inclusive, are of great interest to the collector. 
 
22 
 
 shores could be better seen, thus enabling 
 the collector to get the desired material. 
 
 The infusoria are the most widely dis- 
 tributed of any class of microscopic life. 
 Infusions of every sort and kind, and 
 waters of every degree of purity, contain 
 them.* Even falling rain and dew provide 
 a home for extensive series. Certain 
 classes are found only in salt and brakish 
 water, and others in putrid infusions. 
 These may be excluded as beyond the 
 limits of the present inquiry. 
 
 Weedy ponds, or weedy nooks in reser- 
 voirs or lakes, and slowly running water, 
 are the most favorable collecting fields for 
 the species we are at present interested in. 
 In such places one may profitably examine 
 finely divided living plants for specimens 
 of the more sedentary species, such as the 
 Ciliata Flagellata. Dead and decaying 
 leaves in the water should be examined for 
 colonies of Vorticella and Euglena. Cer- 
 tain of the entomostraca, as, for instance, 
 Cyclops and Canthocamptus, and the higher 
 
 * Kent's " Manual of the Infusoria," 64 (" The Distribu 
 tion of the Infusoria,") p. 107, and following. 
 
23 
 
 crustacean forms, Assellus and Gamarus, 
 are likely to be covered with some of the 
 parasitic species. 
 
 For the collection of the infusoria one 
 needs most a dipping-bottle, and some 
 means of reaching beyond arm's-length, 
 together with several small bottles to 
 which to transfer the collections from the 
 dipping-bottle. 
 
 A dipping bottle, as used by the author 
 in his collecting -trips, consists of an 
 ordinary two-ounce morphine bottle, fast- 
 ened to the end of a walking-stick by a 
 strong rubber band around the neck of 
 the bottle, with the end of the stick pass- 
 ing between the band and the neck. For 
 concentrating the dippings, a large-mouthed 
 twelve-ounce bottle with two funnels, one 
 of them small enough, when the stem is 
 thrust through a small hole in the cork, to 
 pass down into the body of the bottle in 
 an inverted position, has been used. The 
 mouth of this funnel is covered with a 
 piece of light cotton cloth. The other 
 funnel, which is larger, also has its stem 
 passing through the cork, but in an up- 
 
24 
 
 right position. The dippings are poured 
 into the upright funnel, pass down through 
 the stem of same into the bottle, where 
 the inverted cloth-covered funnel acts as a 
 strainer, allowing the water to flow up out 
 of the bottle, but retaining whatever of 
 microscopic life may have been brought 
 up by the dipping.* This apparatus has 
 been found of use on several occasions 
 where the particular organism desired ex- 
 isted only in small numbers, and sparingly 
 distributed through a considerable volume 
 of water. 
 
 The rotifera may be collected by means 
 of the collecting-bottle and concentrating 
 apparatus just described. They are likely 
 to be found in all varieties of water, and a 
 formal enumeration of their habitats would 
 transcend the limits of the present chapter. 
 The . reader is referred to Hudson and 
 Gosse's f new work for detailed information 
 on this point. 
 
 * For illustrations of this device see " Practical Micro- 
 scopy," by Geo. E. Davies, second edition, p. 130, chapter 
 on " Collection of Objects." 
 
 t " The Rotifera, or Wheel Animalcules," eo by C. T. 
 Hudson, assisted by P. H. Gosse. Chapter iv., on the 
 " Haunts and Habits of the Rotifera." 
 
25 
 
 Certain worms of the class Annulata are 
 indicative of badly contaminated sewage 
 waters. Where it is desired to collect and 
 preserve them for purposes of comparison, 
 they may be found in any stream receiving 
 sewage, and are easily obtained by use of 
 a simple dipping-bottle. 
 
 For collecting the entomostraca from 
 ponds, lakes, and reservoirs, the dipping- 
 net is indispensable.* This is made by an 
 iron ring, about one foot in diameter, 
 attached by a strong ferrule to a pole ten 
 to fifteen feet in length. The iron ring 
 has a bag fitted to it (a flour-sack answers 
 every purpose), and the pole should be 
 strong enough to allow of lifting some 
 considerable amount of water. This net 
 may be used, not only in shallow water 
 and among weeds, but also for towing 
 behind a boat in deeper water.f It is 
 emptied by allowing it to drain through 
 
 * " A Final Report on the Crustacea of Minnesota," by 
 C. L. Herrick, & 8 b, chapter iv., on " Collecting, Preservation, 
 and Miscellaneous Notes." 
 
 t For illustration of modification of this net, especially 
 adapted for towing in deep water, see " Practical Micro- 
 scopy," chapter on " Collection of Objects," above referred 
 to. 89 
 
26 
 
 the meshes of the cloth, and then, when 
 only a small amount of water is left in the 
 bottom, transferring the same to a wide- 
 mouthed bottle by quickly inverting the 
 bag. 
 
 The above covers the principal methods 
 and appliances for collecting. Other meth- 
 ods will, no doubt, suggest themselves as 
 one progresses in biological studies. 
 
 In concluding the subject of collecting, 
 it is desired to impress upon the reader the 
 importance of keeping a full and complete 
 record of everything relating to each col- 
 lection, as, for instance, where it was found, 
 and under what general and special condi- 
 tions. Information of this kind will pos- 
 sess great interest when making a final 
 judgment of the value of any given sample 
 for sanitary purposes. For such a record 
 the author usually carries several small 
 blank gummed labels, such as are used for 
 slides. These are numbered, and one is 
 pasted to each bottle ; the number being 
 made to correspond with that of the entry 
 in a small memorandum-book, which com- 
 pletes this part of the collecting-record. 
 
27 
 
 These numbers can be carried in a series 
 through an entire season's work, and 
 further used for the record of the exam- 
 ination in the laboratory or at home. 
 
 PRESERVATION OF MATERIAL. 
 
 Having collected the material, it becomes 
 an exceedingly important question how to 
 best preserve it for future reference. Much 
 ingenuity has already been expended in 
 devising methods of separating micro- 
 scopic material from the various degrading 
 contaminations gathered with the original 
 collections, and much still remains to be 
 done. 
 
 Diatoms and desmids are usually sepa- 
 rated by methods depending essentially 
 upon differences in the specific gravity of 
 various objects. For detailed description 
 of such methods, and the necessary appa- 
 ratus, the reader is referred to Nave's " Col- 
 lector's Handy-Book," already mentioned.* 
 
 The smaller species of diatoms, when 
 
 * Also to " Practical Microscopy," pp. 138, 139-288-290. 
 See also article " Diatomaceae," in fourth edition of" Micro- 
 graphic Dictionary " ^ (" Collection "), p. 252. 
 
28 
 
 living, may be separated by placing the 
 material containing them in a shallow dish, 
 with a little water, and laying over them a 
 thin cloth. The tendency to move toward 
 the light, which seems inherent in all these 
 minute organisms, will cause them to creep 
 through the meshes of the cloth, appearing 
 on the upper side, frequently in such quan- 
 tities as to be easily scraped off with a thin 
 knife, and entirely free from the degrading 
 material. 
 
 FILAMENTOUS ALG^. 
 
 The filamentous algae can be cleansed by 
 washing ; but when in fruit this needs to be 
 done with the greatest possible care, other- 
 wise the operator is certain to lose that 
 which he most desires to retain. Indeed, 
 certain of them are so delicate, when in 
 fruit, that the slightest disturbance will 
 inevitably cause them to break up; and, as 
 a measure of safety, it is often best to 
 mount them without any attempt at wash- 
 Hig. This becomes especially importanj; 
 when we consider that it is absolutely 
 impossible to identify numerous species 
 
29 
 
 of fresh-water algae except when in fruit; 
 and as the fruiting season with many spe- 
 cies is very short, extending over only a 
 few clays in some cases, we are obliged to 
 accept one horn or the other 'of the 
 dilemma, either to run the chances of 
 losing that which makes certain the iden- 
 tification, or else to get into our mounts a 
 little dirt. In many cases we are obliged 
 to accept the dirt with algae as inevitable, 
 and run no chances. 
 
 FRESH-WATER ALGJE FLUID. 
 
 Until a few years ago no satisfactory 
 medium for mounting the fresh-water algae 
 was known in this country, and even now 
 there seems to be a chance for slight 
 improvement. King's Fresh-Water Algae 
 Fluid * has, however, the merit of preserv- 
 ing many species almost perfectly, and all 
 species fairly well. Its chief fault is that 
 the endocrome in some of the algae shrink 
 slightly, and unfortunately such shrinking 
 usually has the effect of obscuring just the 
 
 * Prepared by Rev. John D King. 
 
30 
 
 features one desires most to see. On the 
 other hand, it preserves the chlorophyl 
 perfectly, so that even after the lapse of 
 years the green color remains as distinct 
 as on the day of collection. Mr. King has 
 stated * that desmids mounted four years 
 ago are still as bright as when first mounted. 
 This is an excellent test of the preservative 
 properties of this fluid, as the desmids are, 
 on the whole, the most delicate, so far as 
 the chlorophyl is concerned, of all the 
 fresh-water algae. 
 
 The following is the formula for this 
 fluid : t 
 
 Camphor water 
 Distilled water 
 Glacial acetic acid* 
 Crystal copper chloride 
 Crystal copper nitrate 
 
 50.00 grammes. 
 50.00 grammes. 
 
 0.50 grammes. 
 
 0.20 grammes. 
 
 0.20 grammes. 
 
 This should be filtered after solution. 
 The following preservative fluid is sim- 
 
 * Private communication. 
 
 t This is really Petit's formula; but it has acquired the 
 name of King's Fluid in this country, from the fact that it 
 was introduced by Mr. King, and first used by him in his 
 classes. 
 
31 
 
 ilar to Mr. King's, and for many species 
 works equally well : * 
 
 Dissolve fifteen grains of acetate of cop- 
 per in a mixture of four fluid ounces of 
 camphor water and four fluid ounces of dis- 
 tilled water, add twenty minims of glacial 
 acetic acid and eight fluid ounces of 
 t Price's glycerine, and filter. 
 
 This fluid is said to answer well for pre- 
 serving algse in tubes, and for mounting. 
 
 MOUNTING IN FLUIDS. 
 
 The use of a fluid medium, however 
 well it may preserve the distinctive fea- 
 tures of the algse, has the serious disadvan- 
 tage that the mounts, if not made with the 
 greatest care, are liable to leak, and this 
 means, of course, the loss of the prepara- 
 
 * This is Morehouse's formula as given in vol. iv. of 
 The American Monthly Microscopical Journal. Mr. 
 Morehouse suggests varying the specific gravity by cluuige 
 of proportion of glycerine; and systematic study in this 
 direction would probably result in the finding of a series 
 of fluids adapted to nearly all the fresh-water algae. 
 Hantzsch's method, described in Nave's "Handy-Book," 
 is a hint for such a study. 
 
 t Bower's glycerine, which is the standard article in 
 this country, will answer equally well. It is more truly 
 neutral than Price's. 
 
32 
 
 tion. Mr. King has experimented with 
 cements to meet this difficulty, and his 
 Lacquer Cell and Finish * is claimed to 
 furnish a tolerably safe remedy. With 
 this cement thin cells are run on slides 
 with a turn-table ; and after drying, the 
 mounting may be proceeded with in the 
 usual manner. 
 
 Mr. King's directions for mounting in 
 fluids are as follows : f 
 
 1. Allow the cell to harden perfectly. 
 It can be hardened with artificial heat in 
 a few hours. 
 
 2. Bring the cell to an even surface 
 with a fine file, or by warming and press- 
 ure with a smooth, flat metallic or glass 
 surface. 
 
 3. Ring the outer half of the flattened 
 surface with King's White Cement. 
 
 4. Lay on the cover and press it firmly 
 to its place, and be sure that it adheres to 
 the cell at every point. 
 
 * For sale by th Bausch & Lomb Optical Company. 
 The cements may also be obtained directly from Mr. 
 King. 
 
 t These directions are intended by Mr. King to apply 
 particularly to mounting in cells composed of his Lacquer 
 Cell and Finish Cements. 
 
33 
 
 5. To seal the cell, pass it two or three 
 times slowly over the flame of a spirit- 
 lamp to soften it, then apply just pressure 
 enough to the cover to imbed it slightly in 
 the cell. To do this nicely may require a 
 little practice. 
 
 6. Finish with the same, or another 
 color, to fancy. 
 
 It is a good plan to put a ring of the 
 white cement around the edge of the cover 
 before applying the final coat of lacquer 
 finish ; or, if preferred, a good finish can be 
 made with the white cement alone.* 
 
 King's Fluid, diluted with one-half 
 water, answers well as a medium for 
 mounting the infusoria. 
 
 GLYCERINE JELLY. 
 
 Glycerine jelly is also an excellent 
 medium for mounting many species of 
 fresh-water algae. Indeed, Dr. Cooke f con- 
 siders it, on the whole, the best. The gly- 
 cerine jelly has the advantage of making 
 
 * For formula for King's cements, see Behrens' " Guide 
 to the Microscope in Botany," ^ p. 235, 236. 
 
 t " British Fresh-Water Alga," by M. C. Cooked 
 
34 
 
 mounts safe from the danger of leaking, 
 but delicate filaments are badly distorted. 
 It has been used, however, for Nostoc and 
 Ulothrix with good results. 
 
 Mounting with glycerine presents some 
 difficulties of technique ; and the following, 
 on glycerine jelly and its use in mount- 
 ing, is from Mr. King, who is an expert in 
 its use. Mr. King says : * 
 
 " I put up a jelly after Kaiser's for- 
 mula, t with the improvement of a spe- 
 cially selected gelatine made from the 
 swimming bladder of the sturgeon, that 
 requires less glycerine, and is less objec- 
 tionable, than any other I have ever used. 
 ... It is a splendid jelly, and will stand 
 hot weather without melting. 
 
 "As to my methods of using, I melt it 
 on the slide, in the quantity needed to 
 nearly fill the cell, placing the object 
 where I want it, and taking off every air- 
 bubble that can be seen with the naked 
 eye ; after which it is put by and allowed 
 to harden. I then melt a little of the 
 jelly on the cover glass, breathe hard on 
 
 * Private letter. t Behrens', 85 p. 220. 
 
35 
 
 the slide, turn the cover over quickly and 
 put it on the object, being sure that no air- 
 bubbles are caught under the cover. I 
 then put on a delicate clip, pass it over a 
 spirit-lamp till it warms enough to come 
 to its bearings ; let it harden ; clean off 
 the greatest part of the jelly with a pine 
 stick sharpened, after which the slide is 
 put into a dish of water and washed off 
 clean with a small bristle-point brush. 
 The slide is then carefully wiped dry 
 and finished." * 
 
 -In using glycerine jelly, the author has 
 found it desirable to have the jelly one or 
 two inches deep, in a five or six inch test- 
 tube. This tube is stopped with a cork, in 
 which is secured a glass rod about one- 
 eighth of an inch in diameter, drawn to a 
 blunt point at the lower end, and of such 
 length as to reach just short of the bottom 
 of the tube. In mounting, the object is 
 first placed in position in the cell, and 
 having warmed the jelly in the test-tube, 
 
 * Additional hints on mounting In glycerine jelly may 
 be found in " Practical Microscopy," 89 chapter xiii., " The 
 Preparation and Mounting of Objects," and in Behrens' 
 " Guide to the Microscope in Botany." 85 . 
 
over the chimney of the lamp, which fur- 
 nishes illumination for the microscope, 
 the glass rod with a drop of the melted 
 jelly upon it is brought to the object. Air- 
 bubbles are removed, and the balance of 
 the operation proceeded with substantially 
 as described by Mr. King. This is found 
 less troublesome than the cutting of small 
 pieces of the jelly, as practised by Mr. 
 King, and the difficulty of getting rid of 
 the air-bubbles from the melted jelly is no 
 greater. . 
 
 KILLING AND FIXING. 
 
 * Glycerine and glycerine jelly are also 
 the most useful mediums for mounting the 
 entomostracan Crustacea. They work ad- 
 mirably for all the species included in the 
 order Copepoda, but for the Cladocera they 
 shrink the tissue unless it is first sub- 
 mitted to special treatment ; namely, the 
 crustacean should be instantaneously killed 
 with some reagent, which, while producing 
 death, leaves the body in all its parts en- 
 
 * " Final Report on the Crustacea of Minnesota," by C. 
 L. Herrick.< r ' 8 b 
 
37 
 
 tirely unaltered. For this purpose osmio 
 acid has been most used ; but this is not 
 entirely successful, due to the fact that it 
 discolors the tissue. 
 
 Prof. Herman Fol has discovered that 
 muriate of iron (ferric perchloride) pro- 
 duces not only instantaneous death, but a 
 fixation of all the parts, with very little 
 discoloration or shrinkage.* According to 
 Herrick, the alcoholic solution is diluted 
 to about two per cent, and applied to a 
 small quantity of water, in which the ani- 
 mal is swimming. The water is poured 
 off and the crustacean washed with seventy 
 per cent alcohol, to which a few drops of 
 nitric acid may be added to remove the 
 iron salts. 
 
 Osmic acid is highly recommended by 
 Kent t for killing and fixing infusoria. By 
 its use he says they may be preserved as 
 naturally as though living ; and the matter 
 of securing permanent mounts of nearly all 
 types of infusoria becomes merely a ques- 
 
 * C. L. Herrick (loc. c.). 
 
 t "Manual of the Infusoria." 64 " Preservation of the 
 Infusoria," p. 113. 
 
38 
 
 tion of patient manipulation. Coloring re- 
 agents may also be used in connection with 
 the osmic acid, so that all the structures, 
 such as Cilia and Flagella, the internal 
 endoplast, and in Euglena the colors also 
 are preserved; "the animalcules, excepting 
 for the absence of motion, being scarcely 
 distinguishable from the living organisms." 
 
 For killing and fixing hydra, Huxley 
 and Martin * recommend first placing the 
 animal in a small quantity of water, and 
 after the hydra has extended its tentacles, 
 adding boiling water. 
 
 The author has used for this purpose the 
 muriate of iron, as recommended by Fol, 
 for the Crustacea, and was successful in 
 killing the hydra in an extended condition ; 
 but the structure soon broke down, so 
 that, from present information, it appears 
 that the muriate of iron cannot be used 
 where permanent preparations of hydra 
 are desired. 
 
 The rotifera may be mounted in glycer- 
 ine jelly, and for killing and fixing, both 
 
 * " Practical Biology," 101 by T. H. Huxley, assisted by 
 H. N. Martin ; chapter, " The Fresh-Water Polypes," p. 104. 
 
39 
 
 osmic acid and muriate of iron have been 
 -found to work well. 
 
 The foregoing includes a few of the 
 elementary facts. Whoever wishes to pur- 
 sue the subject extensively, may find 
 abundant references to literature in the 
 list following Part II. 
 
PART II. QUANTITATIVE., 
 
 The Microscopical Examination of 
 Potable Water. 
 
 LIMITATION OF THE SUBJECT. 
 
 IN a paper on " Recent Progress in Bio- 
 logical Water Analysis/ 7 21a by Prof. Wm. 
 T. Sedgwick, of the Massachusetts Insti- 
 tute of Technology, is found a clear defi- 
 nition of the classes of micro-organisms as 
 occurring in potable waters. The defini- 
 tion there given has been again used by 
 Prof. Sedgwick, in a " Report on the Bio- 
 logical Work of the Lawrence Experiment 
 Station," 21d as published in 1890 ; and it 
 may be taken as representing the latest 
 views, both in this country and abroad, in 
 relation to the classification of this sub- 
 ject. 
 
 40 
 
41 
 
 Tabulated, it assumes the following 
 form : 
 
 (1. MICROSCOPICAL, OR- 
 GANISMS. 
 
 a. Not requiring spe- 
 cial cultures. 
 
 6. Easily studied with 
 the microscope. 
 
 c. Microscopic in size, 
 
 or slightly larger. 
 
 d. Plants or animals. 
 
 MICRO-ORGANISMS. 
 
 Plants or animals, 
 either in visible or barely 
 visible to the naked 
 eye. 
 
 2. BACTERIAL ORGAN- 
 ISMS. 
 
 a. Requiring special 
 
 cultures. 
 
 b. Difficultly studied 
 
 with the microscope. 
 
 c. Microscopic or sub- 
 
 microscopic in size. 
 \ .d. Plants. 
 
 The present monograph will deal exclu- 
 sively with the microscopical organisms, 
 without reference to the bacterial organ- 
 isms. The latter have been treated so 
 extensively in the last few years as to 
 greatly obscure the former, with the result 
 of entirely neglecting a promising branch 
 of water analysis. At the present time it 
 is proposed to give a brief history of, and 
 describe a new method of quantitatively 
 determining, the microscopical organisms. 
 
42 
 
 The sanitary significance and relative 
 economic importance of the microscopical 
 forms will be treated in another volume. 
 
 COMPLETE SANITARY ANALYSIS. 
 
 By way of illustrating the importance of 
 a quantitative determination of the micro- 
 scopical organisms, we will briefly discuss 
 the requirements of a complete study of 
 potable water from the sanitary point of 
 view. 
 
 In the first place, it has been proven 
 many times that a single analysis, whether 
 chemical or biological, is entirely without 
 significance in determining the sanitary 
 value of ordinary potable waters. The 
 evidence grows stronger from day to day, 
 that in selecting sources of supply for 
 towns, public institutions, large manufac- 
 turing establishments, or any other place 
 where an error in judgment would involve 
 the health of a number of human beings, 
 complete studies from every possible point 
 of view should be made. If the case in 
 hand is important enough to justify the 
 expense (and it always will be in the case 
 
43 
 
 of large town supplies), the examinations 
 should extend over a whole season, and 
 -in difficult cases over two or more sea- 
 sons. This conclusion is the plain teach- 
 ing of experience, as exhibited in the 
 water supplies of most of the cities of this. 
 country. 
 
 Assuming that a given source is either 
 from a deep pond or lake, or from a creek 
 or river, or involves the impounding of 
 large bodies of water in storage basins, it 
 is premised that the authorities in charge 
 thereof should be possessed of definite 
 information as to a number of points in 
 relation to what may be termed the natural 
 history of the water in question. In order 
 to determine the said points, four distinct 
 lines of investigation may be carried out,, 
 as exhibited in the following : 
 
 1. A STUDY OF THE ENVIRONMENT. 
 
 Including detailed statement of topo 
 graphical and geological conditions of 
 drainage area, together with observations 
 on extent and character of population and 
 industries of the region as special sources 
 
44 
 
 of pollution, with study of normal samples 
 by (2), (3), and (4). 
 
 2. PHYSICAL PROPERTIES. 
 
 This will include a systematic study, 
 with tabulation of results, including a 
 statement of the following : 
 
 a. Depth from which samples are taken. 
 
 b. Temperature. 
 
 c. Specific Gravity for actual depth and 
 
 temperature. 
 
 d. Color. 
 
 e. Turbidity. 
 
 f. Sediment. 
 
 g. Taste and odor. 
 
 3. CHEMICAL ANALYSIS 
 
 a. Albuminoid Ammonia, j J | 
 
 b. Free Ammonia. 
 
 c. Nitrites. 
 
 d. Nitrates. 
 
 e. Chlorine. 
 
 f. Hardness. 
 
 g. Total Solids. 
 
 h. Loss on Ignition. 
 
45 
 
 4. BIOLOGICAL EXAMINATION. 
 
 (4a.) PLANTS. 
 
 1. Chlorophycese. 
 
 2. Cyanophycese. 
 
 3. Diatomaceae. 
 
 4. Fungi, including Bacteria. 
 
 (46.) ANIMALS. 
 
 1. Crustacea. 
 
 2. Vermes (Rotifera etc.). 
 
 3. Polyzoa. 
 
 4. Infusoria. 
 
 5. Rhizopods. 
 
 6. Spongidse. 
 
 7. Miscellaneous. 
 
 (4c.) AMORPHOUS ORGANIC MATTER. 
 
 The microscopical examination will in- 
 clude the determination of everything 
 under (4), except the bacteria. It is thus 
 seen to occupy an important place in a 
 scheme for a complete sanitary analysis ; 
 and having remarked that a large number 
 of examinations made during the last three 
 years by (1) the biologists of the Massa- 
 chusetts State Board of Health, (2) the 
 
46 
 
 biologists of the Connecticut State Board 
 of Health, and (3) by the present writer, 
 have put the matter on a fair working 
 basis, we may proceed to describe the 
 present state of the art of making such 
 examinations : 
 
 HISTORICAL. 
 
 The first systematic examination of a 
 water supply ever made was by Dr^ JHa&all 
 of the water supply of London, in,.43Q. 7 
 The results were given in an illustrated 
 memoir, and stand unique, as furnishing a 
 beginning for scientific study of this im- 
 portant and interesting subject. 
 
 In 1865 L.EadJijQfer 19 published an 
 account of an examination of well waters 
 in Munich. 
 
 In 1&70 Prof. jCqhn, of Breslau, pub- 
 lished a paper on the Microscopical Analy- 
 sis of Well Waters, and indicated clearly 
 therein the significance of such studies. 3 * 
 In this paper Prof. Cohn made the fol- 
 lowing generalizations, which are inter- 
 esting as showing the advanced views to 
 which he had arrived : 
 
47 
 
 1. Diatoms and green algae, Conferva, 
 Protococcus, Scenedesmus, etc., indicate a 
 water to which light lias had access, and 
 one poor in organic matter. 
 
 2. Certain of the larger infusoria, espe- 
 cially the ciliated forms, Nassula, Loxodea 7 
 Urastyla, etc., feed on these algae ; while 
 upon both the infusoria and the algae 
 feed 
 
 3. Entomostracans, Daphnia, Cyclops, 
 Cypris, worms, such as naids and rotif era 
 and insect larvae. 
 
 Prof. Dr. L. Hirt, also of Breslau, pub- 
 lished a paper upon the Principles and 
 Methods of the Microscopical Investiga- 
 tion of Waters, in 1879. 8 
 
 Dr. F. Hulwa published, iiL-1885, 8 * a, 
 paper giving tabulated results obtained by 
 the methods described by Hirt. 
 
 The first edition of Maotkuiald's " Guide 1 
 to the Microscopical Examination of 
 Drinking Water," H appeared in 1,TL The; 
 second edition (1883) contains a method of 
 examination which will be referred to 
 hereafter. 
 
 In 1884 Dr. H. C. Sorby published a 
 
48 
 
 paper on the Detection of Sewage Con- 
 tamination by the Use of the Microscope, 
 arid on the Purifying Action of Minute 
 Animals and Plants. 23 
 
 In FphrnaTvJjggfl, Mr. A_. L. Kca.n 9 pub- 
 lished, in Science, a method of making the 
 quantitative examination of the micro- 
 scopical plants and animals in potable 
 water. 
 
 In Septembej^jLSSO^ Prof^ JYmiam_ T. 
 Sedgwick published, in the paper on Recent 
 Progress in Biological Water Analysis 
 already referred to, 21a what is known as 
 the sand method of making these exami- 
 nations. 
 
 In September. 1890, the present writer 
 published a paper on the Biological Exami- 
 nation of Potable Water. 200 
 
 About Jan. 1, 1891^ the Special Eeports 
 of the MassacTmsetts State Board of 
 Health appeared. 130 Part I., Examination 
 of Water Supplies, contains a method of 
 making the quantitative examination as 
 devised by Mr. G-. H. Parker, formerly 
 biologist to that Board. 13c Part II., Puri- 
 fication of Sewage and Water, contains an 
 
49 
 
 account of the various methods, and an 
 abstract of the literature to the date of 
 publication. 130 
 
 The foregoing are the more important 
 sources of information to be consulted by 
 one desiring to pursue the general subject 
 of the microscopical examination of water 
 historically. The titles of a few other 
 papers and references of less importance 
 may be given. 
 
 Mr. C. M. Vorce published papers on 
 Forms observed in Water Of Lake Erie, 25 in 
 1881 and 1882. These papers contain 
 some useful generalizations as to persist- 
 ency of certain forms in large bodies of 
 water at all seasons of the year. 
 
 Mr. Henry Mills published a paper on 
 the Micro-Organisms, in the Buffalo, N. 
 Y. Water Supply, in 1882. 15 This paper 
 contains an estimate, based on actual obser- 
 vation, of the amount of microscopic life in 
 the Niagara Eiver. 
 
 Dr. C. A. Chamberlain published a paper 
 on Organic Impurities in Drinking Water, 
 in 1883. 3 
 
 Dr. Arthur J. Wolff published a paper 
 
50 
 
 on the Sanitary Examination of Drinking 
 Water, in 1886. 28 
 
 The present writer published a paper on 
 the Micro-Organisms in Hemlock Water, in 
 1888. 20a 
 
 In 1889 Tiemann and Gartner's Chemi- 
 cal, Microscopical, and Bacteriological In- 
 vestigation of Waters 24 appeared. In it 
 may be found an abstract of the useful for- 
 eign literature of the subject, and many 
 hints of value in interpreting results. 
 
 THE METHOD OF DR. HASSALL. 7 
 
 Dr. Hassall, although the first to apply 
 the microscrope to the determination of the 
 organic constituents of water, has not in 
 any of his papers made it clear just how 
 he obtained his results ; though we may 
 infer from what he has said, that his pro- 
 cess was, essentially, to examine a drop of 
 the sediment contained in the bottom of a 
 test-tube, in which a sample of the water 
 had been allowed to stand long enough for 
 thorough sedimentation to occur. 
 
51 
 
 METHODS OF THE GERMAN BIOLOGISTS. 
 
 Radlkofer 19 leaves us entirely in the 
 dark as to the methods used in his examin- 
 ation of the well-waters of Munich ; but <^/ 
 we may infer that his method, like that of 
 Cohn in the examination of the waters of ^ 
 Breslau, consisted in a direct microscopical JK 
 study of either a few drops of water or of 
 the sediment. 
 
 Hirt, in his paper, recommends the fol- 
 lowing course of procedure : 8 
 
 1. The direct observation of fresh sam- 
 ples of the water, a drop at a time ; as \ 
 many as twenty or thirty drops being suc- 
 cessively scrutinized. 
 
 2. An examination of the sediment ^ 
 obtained after standing at least two days. 
 
 3. A study of the surface pellicle, 
 should any form after the sample has 
 stood for a few days.* 
 
 In this way Hirt finds it necessary to 
 make as many as thirty to forty examina- 
 
 * This third course of procedure was used previous to 
 the introduction of the modern methods of bacteriology, 
 and was, until about 1881, the approved method of studying 
 the bacteria in their relation to potable waters. 
 
52 
 
 tions before completing the study of any 
 given sample. 
 
 THE METHOD OF DR. MACDONALD. 14 
 
 For this method of examination tall, 
 -cylindrical glass vessels with small rounded 
 bottoms are recommended. In the absence 
 of the special vessels a litre or half-litre 
 measuring-glass may be used. For the 
 examination of a sample, one of the tall 
 glass vessels is first filled with water, 
 after which a circular disk of glass, resting 
 on a horizontal loop at the end of a long 
 aluminium wire is lowered to the bottom. 
 The tall glass is covered and set aside for 
 twenty-four or forty -eight hours, as the case 
 may be. After standing the specified time 
 the water is siphoned off with tubing, 
 leaving only a thin stratum over the disk, 
 which is then raised and laid upon blot- 
 ting-paper to remove surplus moisture. 
 The disk is then covered with a large cover 
 glass, and transferred at once to the stage 
 of the microscope for direct examination- 
 
 Dr. MacDonald further says, an ordinary 
 'watch-glass may in some cases be substi- 
 
53 
 
 tuted for the disk, with advantage, as being 
 less likely to permit the loss of sediment 
 by overflow. Another plan suggested is 
 to siphon off the water until only enough 
 remains to just permit the sediment to be 
 shaken up with it, and turned into a coni- 
 cal-shaped glass, from which, after standing 
 for a short time, portions may be taken for 
 -examination. By proceeding as outlined in 
 the foregoing, a judgment could be formed 
 as to the amount and kind of the organic 
 impurity present. Independent, however 
 of the impossibility of establishing numeri- 
 cal relations, the practical difficulties of 
 examinations on either the plain glass 
 disk or in the curving watch-glass are con- 
 siderable. The chief sources of possible 
 error in final judgment may be enumerated 
 as follows : 
 
 1. During the time of standing for 
 purpose of sedimentation, a diminution of 
 the number and kind of species originally 
 present may be expected to take place, by 
 reason of one form eating another up. 
 
 2. Impossibility of knowing that at the 
 
54 
 
 end of the time allowed for sedimentation, 
 all the forms originally present in the 
 sample have fallen to the bottom, and are 
 present in' the sediment. 
 
 3. In using the plain glass disk, the 
 liability of losing some of the sediment 
 when placing the cover-glass. 
 
 4. In using the watch-glass, difficulty 
 of fully examining the sediment, on account 
 of the curved bottom. 
 
 5. In taking drops of sediment with a 
 pipette for examination on a slide ; uncer- 
 tainty as to whether samples containing all 
 the forms present in the sediment are 
 obtained. 
 
 Dr. MacDonald's work must, neverthe- 
 less, be considered of the greatest possible 
 value. His general definition of technique 
 is good, especially the directions in refer- 
 ence to collection of samples, and methods 
 of insuring microscopical cleanliness at 
 every stage of the operation. His book 
 should be in the hands of every person 
 using the microscopical method. 
 
55 
 
 THE METHOD OF DR. H. C. SORBY. d 
 
 111 1884 Dr. H. C. Sorby, of England, 
 /iade a study of different samples of river 
 IJid sea water, with the object of ascertain 
 jng the number per gallon of the various 
 small animals large enough to be held back 
 by a sieve with meshes about one two-hun- 
 dredths of an inch in diameter. Amounts 
 of water varying from ten gallons down- 
 wards, according to the number of forms 
 present, were passed through such a sieve. 
 The retained organisms were subsequently 
 washed off into a dish, and an enumera- 
 tion made, just how, Dr. Sorby does not 
 state. The forms which he was studying 
 were comparatively large (Cyclops and 
 other Entomostracan Crustacea) ; and an 
 enumeration could be easily made, either 
 in a watch-glass with a low-power object- 
 ive of considerable penetrating power, or 
 in a large flat cell of special construction, 
 by the use of an ordinary hand magnifier. 
 Dr. Sorby gives numbers per gallon of the 
 various forms found in different waters ; 
 and we may conclude from what he has said. 
 

 that so far as the larger microscopical 
 forms are concerned, he considered that a 
 fairly accurate method of enumeration had 
 been used. He also enumerated the infu- 
 soria, and states, that at low water in the 
 Medway, above Chatham, in the first half 
 of June, the average number per gallon has 
 been about 7.000, but sometimes as many 
 as 16,000. The average size of the infu- 
 soria so enumerated, he states at one one- 
 thousandth of an inch. Clearly a much 
 smaller mesh than was used for the ento- 
 mostraca, and special methods of gathering 
 would be required ; but just how all this 
 was accomplished Dr. Sorby has failed to 
 tell us. The paper is, however, suggestive 
 as to possibilities of future results, and 
 may be profitably consulted by the student 
 of the advanced methods. 
 
 METHODS USED IN THE UNITED STATES 
 PRIOR TO 1889. 
 
 Of the several papers which have ap- 
 peared in this country previous to 1889, it 
 may be said, in a general way, that the 
 authors of all have apparently gone no 
 
57 
 
 further towards a quantitative determina- 
 tion of the microscopical organisms than 
 to examine a sediment usually obtained by 
 allowing the water to flow through a 
 strong cotton cloth. When public water 
 supplies were the subject of examination, 
 a bag of such material was attached to an 
 ordinary laboratory, or domestic cock, and 
 the water simply allowed to run, until, as 
 a matter of judgment, enough had been 
 filtered through the cloth to insure a pro- 
 lific sediment. The flow being stopped, 
 the bag was removed, and, after the water 
 still contained in it had drained through, 
 the bag was turned wrong side out, and the 
 organisms removed by dabbling and lightly 
 washing in a small amount of water from 
 the supply under examination, contained 
 in a clean shallow dish. After so re^aov- 
 ing the organisms' from the cloth ? the 
 water containing them was turned into a 
 conical-shaped glass, from which, after 
 subsidence of the organisms to the bottom, 
 samples were taken by the use of a pipette 
 for examination in the usual manner on a 
 slide. In this way the results, as detailed 
 
58 
 
 by Mr. Vorce, 25 Mr. Mills, 15 and by the 
 members of the Microscopical Section of 
 the Rochester Academy of Science, as de- 
 tailed in the paper published by the pres- 
 ent writer 20a in 1888, were obtained. 
 
 THE METHOD OF MR. G. H. PARKER. 13c 
 
 In 1888 Mr. Parker, as Biologist to the 
 Massachusetts Board, worked out and ap- 
 plied a method for examination somewhat 
 different from any of the preceding. A 
 small piece of cloth is taken, and firmly 
 tied to the stem of a common glass funnel, 
 in such manner that the sample "of water 
 when poured into the funnel would filter 
 through only that portion of the cloth di- 
 rectly in front of the end. All being 
 arranged, two hundred cubic centimetres 
 of tRe water to be examined are poured 
 into the funnel. At the end of the filtra- 
 tion, the organisms contained in the water 
 are found collected on the cloth on a small 
 area of the size of the bore of the stem of 
 the funnel. The cloth is now removed; 
 and inverted over a glass tube of some- 
 what greater area than the circular spot 
 
of arrested organisms. The tube is so 
 held that the end with the inverted cloth 
 is just above the middle of an ordinary 
 glass slide ; and a sharp blast of air 
 through the tube dislodges the sediment 
 with a small amount of water upon the 
 slide, where, after covering with a cover 
 glass, it may be examined under the mi- 
 croscope. Mr. Parker states, that this 
 method gives good results, so far as de- 
 termining the kind of organisms is con-- 
 cerned ; but, from a quantitative stand- 
 point, it yields only rough approximations. 
 The principal sources of inexactness 
 are : 
 
 1. A few of the smaller organisms pass 
 through the cloth. 
 
 2. Impossibility of removing all the 
 organisms from the cloth to the slide. 
 
 3. Difficulty of distributing the sedi- 
 ment on the slide equally enough to per- 
 mit accurate estimates of the number of 
 the organisms. 
 
 The method of Mr. Parker has been 
 known as the *' cloth method/ 7 and is so 
 referred to in the Massachusetts reports. 130 
 
THE METHOD OF MR. A. L. KEAN. 9 
 
 In this method a known quantity of 
 water (Mr. Kean says 100 cubic centi- 
 metres is a convenient unit) is put into a 
 funnel, in the tube of which is half an 
 inch in depth of coarse sand (24 to 30 
 grains to the inch). The sand is held in 
 place by a plug of wire gauze in the foot 
 of the funnel, which, while allowing the 
 water to pass, still holds the sand back. 
 After all the water has passed through, the 
 plug is removed, and one cubic centimetre 
 of distilled or freshly filtered water thrown 
 into the stem of the funnel, by means of a 
 pipette. This washes the sand and con- 
 tained organisms down into a watch-glass, 
 placed to receive it. The grains of sand 
 sink to the bottom, leaving the organisms 
 mostly suspended in the water. Stirring 
 produces more even distribution, and lib- 
 erates any caught between the grains of 
 sand. A cell of one cubic millimetre vol- 
 ume is provided, and to it a portion of the 
 water from above the sand in the watch- 
 glass, sufficient to just fill it, is transferred 
 
61 
 
 for examination. The organisms contained 
 in the cell are then counted, and from the 
 result the total number in the original 
 sample computed. 
 
 This method was described by Mr. Kean 
 in his original communication 9 in consid- 
 erable detail ; and to him, therefore, per- 
 tains the credit of having first published 
 a quantitative method of determining the 
 microscopical organisms in water. Credit 
 for first using such a method seems to per- 
 tain to Dr. H. C. Sorby, though with what 
 measure cannot be determined in the ab- 
 sence of the detail. 
 
 The chief defect of Mr. Kean's method 
 is in the smallness of the amount actually 
 examined, a difficulty which limits the 
 accuracy of the method in four ways : 
 
 1. The amount of one cubic millimetre 
 is so small that important forms are easily 
 overlooked. 
 
 2. The cubic millimetre is only the one 
 one-thousandth part of the cubic centi- 
 metre, and the necessity of multiplying by 
 1,000 leads, with an error of one in the 
 count to an error of 1,000 in the result, as 
 
62 
 
 applying to the one cubic centimetre in the 
 Watch-glass. With an original quantity 
 of 100 cubic centimetres, this again leads 
 to an error of 10, per cubic centimetre, in 
 the final result. 
 
 3. If only one of a given form appears 
 in the count, it must be interpreted as in- 
 dicating 1,000 in the one cubic centimetre 
 in the watch-glass, whereas it may possi- 
 bly have been the only one there. 
 
 4. The impossibility of getting in the 
 reductions a number between and 10 per 
 cubic centimetre. To get one per cubic 
 centimetre would require the filtering of 
 1,000 cubic centimetres (one litre) in every 
 case. 
 
 THE SAND METHOD OF PROFESSOR 
 SEDGWICK. 21a ' 13c 
 
 The various practical objections to the 
 method of Mr. Kean having been de- 
 veloped by comparison and experiment, 
 Prof. Sedgwick, in the spring of 1889, 
 worked out what is known as the sand 
 method. In this, the controlling idea was 
 to provide a remedy for the excessively - 
 
63 
 
 high results attained by the method of 
 Mr. Kean. The filtration is made as iix 
 Mr. Kean's method, 100 cubic centimetres 
 being likewise the quantity of water oper- 
 ated upon. A cell 50 millimetres in 
 length, 20 millimetres in width, and about 
 2.5 millimetres in depth is provided. This 
 cell is formed by cementing a brass border 
 upon an ordinary three by one glass slide. 
 Before setting this brass border, the upper 
 surface of the slide is ruled into 1,000 
 squares, each one millimetre in area. The 
 filtration being completed, the sand, to- 
 gether with the organisms, is washed by a 
 small stream from a wash-bottle contain- 
 ing distilled water, into the cell just de- 
 scribed, where they are evenly distributed 
 over the bottom by the use of a needle or 
 fine wire. We now have the organisms 
 from 100 cubic centimetres of water evenly 
 distributed in a cell of 1,000 square mil- 
 limetres area ; and theoretically it would 
 be possible, by using a low-power object- 
 ive, and taking in order each square 
 millimetre of the area, to actually count 
 all the organisms in the- cell ; that is to 
 
64 
 
 Say, to count all the organisms in the one 
 hundred cubic centimetres of water oper- 
 ated upon. In practice, however, the 
 counting of 1,000 squares would consume 
 so much time as to make the labor of the 
 counts a serious burden. Moreover, it 
 was found by experience that a count of 
 twenty representative squares gave a fairly 
 accurate average of the whole ; and twenty 
 squares was accordingly adapted as the 
 unit count. In this way 50 is obtained as 
 a factor of multiplication, instead of 1,000, 
 as in the method of Mr. Kean. By count- 
 ing a larger number of squares a still 
 smaller factor results ; thus fifty squares 
 counted gives a factor of multiplication of 
 only 20. 
 
 For further details of this interesting 
 and valuable advance in methods of making 
 the microscopical examination of water, 
 the reader is referred to either Prof. 
 Sedgwick's original paper, 21a or to his 
 further discussion of it in the Massachu- 
 setts Board's Special Report. 130 
 
65 
 
 THE PERFECTED SEDGWICK-KAFTER 
 METHOD. 
 
 In June, 1889, the present writer organ- 
 ized, at the instance of Desmond Fitz- 
 Gerald, C. E., Resident Engineer of the 
 Western Division of the Boston Water 
 Works, a series of investigations of the Bos- 
 ton Water Supply. Considerable trouble 
 has occurred at various times in this water 
 supply, by reason of excessive growths, at 
 irregular periods, of microscopical organ- 
 isms ; and the Boston Water Board deemed 
 it desirable to study the matter broadly 
 enough to presumably make some definite 
 addition to existing knowledge of the 
 laws governing such growths. A small 
 laboratory was erected, the necessary ap- 
 pliances secured, and arrangements made 
 for a systematic study extending, possibly, 
 over a number of years'. In July, Prof. 
 Sedgwick kindly demonstrated his sand 
 method to Mr. FitzGerald and the author in 
 his laboratory, and finished one of his count- 
 ing plates. The author's previous studies 
 had made him familiar with the method 
 
of Dr. Mac Don aid and the faw American 
 workers, and he was .able to appreciate the 
 advanced ground reached by Prof. Sedg- 
 wick. His sand method, while far in ad- 
 vance of that of any other worker, seemed, 
 however, somewhat unsatisfactory in this, 
 that the sand and organisms are both 
 allowed to pass into the cell together; and 
 inasmuch as the finest grains of sand are 
 much larger than many of the organisms, 
 it follows that the enumeration, however 
 carefully made, is only an approximation 
 to the number actually present, and usually 
 falls short of 'the number present. 
 
 In the method as now used by the 
 author, the sand is supported upon a 
 plug of wire cloth, placed at the lower 
 end of the funnel stem. After placing the 
 plug, the sand is run into the funnel, 
 lightly pressed to place with a glass rod, 
 and from 20 to 40 cubic centimetres of 
 freshly filtered water allowed to run 
 through, in order to insure thorough set- 
 tling of the sand before actually begin- 
 ning the nitration. The amount of water 
 to be filtered is gauged by the number of 
 
67 
 
 organisms which it contains, as ascertained 
 by preliminary inspection. Generally, 
 
 5? 
 P 
 
 however, as large a quantity should be 
 used as can be conveniently filtered with- 
 out clogging the sand so much as to render 
 the completion of the process too pro- 
 
68 
 
 longed ; and for ordinary samples 500 cubic 
 centimetres has been fixed upon as the 
 proper amount. In the -case of very pure 
 waters a larger amount will be desirable ; 
 and, for such, 1,000 cubic centimetres may 
 be adopted as a convenient unit. 
 
 Experience indicates that however care- 
 fully the sand may be placed, the filtration 
 at the beginning will not be as complete 
 as further on ; and, in order to insure the 
 certain removal of all the smaller organ- 
 isms, the first 100 to 150 cubic centimetres 
 of the filtrate is returned to the funnel 
 and passed through the sand a second 
 time. The funnel is allowed to stand 
 until the completion of the filtration, when 
 it is found on examination of the filtrate 
 that nearly every organism has been re- 
 moved," and we have the result that the 
 organisms originally contained in the 500 
 cubic centimetres of water are all in the 
 sand at lower end of funnel stein. The 
 plug of wire cloth is now removed, and 
 the sand and contained organisms washed 
 with 5 cubic centimetres of freshly filtered 
 water, run from a 5 cubic centimetre pipette, 
 
69 
 
 into a 5 or 6 inch test-tube. The test-tube 
 is slightly shaken, in order to wash all the 
 organisms clear from the sand. The sand, 
 by reason of greater specific gravity, sinks 
 quickly to the bottom, leaving the organ- 
 isms distributed through the water. At 
 the instant of the completion of the set- 
 tling of the sand the supernatant water 
 is turned into another smaller test-tube, 
 leaving the clean sand at the bottom of 
 the first tube. We now have the organ- 
 isms from 500 cubic centimetres of water 
 concentrated into 5 cubic centimetres in 
 the second tube, from which, after slight 
 stirring, to insure uniform distribution, 1 
 cubic centimetre is taken with a 1 cubic 
 centimetre pipette, and transferred to a 
 cell 50 by 20 millimetre area, and exactly 
 1 millimetre in depth. Such a cell, of 
 course, contains 1,000 cubic millimetres, or 
 1 cubic centimetre. The top of the metal 
 cell is ground perfectly smooth, and with 
 a little practice one can float a thick cover- 
 glass to place without losing a drop. 
 
 The next step is the enumeration. This 
 is accomplished by transferring the cell to 
 
70 
 
 the stage of a microscope, the eye-piece of 
 which is fitted with a micrometer, so ruled 
 as to cover, with a given objective and 
 fixed tube length, a square millimetre on 
 the stage. The microscope itself is fitted 
 with a mechanical stage with millimetre 
 movement in both directions ; and for this 
 purpose certain simple additions have been 
 made to the new mechanical stage of the 
 Bausch & Loinb Optical Company, by 
 means of which the desired result is 
 obtained at slight expense. The count is 
 made by beginning at one corner of the 
 cell and going systematically over the area, 
 in accordance with such a formula as will 
 insure the count of squares selected from 
 every part of the slide The number of 
 squares actually counted, will depend upon 
 the degree of accuracy which it is desired 
 to attain. It is obviously impossible to 
 count the 1,000 squares composing the 
 entire area of the slide ; and the practical 
 question arises as to just what multiple of 
 1,000 shall be used to secure a correct aver- 
 age. This can only be determined by trial 
 and comparison upon a number of sam- 
 
71 
 
 pies. In any case, not less than 20 squares 
 should be counted, and if time will possi- 
 bly permit, the preference should be in 
 favor of always counting at least 50. 
 
 In order to illustrate the matter, a 
 table has been prepared, which represents 
 the area of the cell divided into 1,000 
 squares. Brief inspection of this table 
 will show the difficulty of obtaining true 
 averages when only 20 squares are counted, 
 and exhibits the value of counting the 
 larger number, in order to obtain true 
 averages. 
 
 The precise millimetre movement of the 
 mechanical stage is considered a matter 
 of considerable importance, and, indeed, 
 insisted upon as an integral part of the 
 method. Without it the tendency will be 
 to sometimes select squares for counting 
 which are contiguous ; while at other times 
 one will pass over squares containing few 
 or no organisms in a search for more pro- 
 lific ones, making, in either case, an error 
 in the final result. By use of the mechani- 
 cal stage, with a definite formula for pass- 
 ing over the slide, personal errors of this 
 
72 
 
 sort are eliminated, leaving only those 
 which are due to irregularity of distribu- 
 tion of the organisms in the water; and by 
 always stirring thoroughly, before taking 
 the portion for examination, with 1 cubic 
 centimetre pipette this error may also be 
 reduced to a small degree, provided as 
 many as 50 squares are counted as the 
 basis of the final average. Additional 
 uniformity of distribution of organisms in 
 the cell, may also be obtained by stirring 
 gently in the cell itself with the pointed 
 end of the pipette, before floating the 
 cover-glass to place ; but the precaution 
 should always be taken in these stirring 
 operations to proceed gently, in order to 
 guard against breaking up unnecessarily 
 the particles of amorphous organic matter, 
 which are nearly always present in any 
 sample of water in which algous growths 
 and decay are taking place. 
 
 The definite estimation of the amor- 
 phous organic matter is a thing of some 
 difficulty ; and in the author's use of this 
 method he has formed a sort of mental 
 standard as to the unit of area covered by 
 
73 
 
 one mass of the amorphous matter. Mr. 
 Geo. C. Whipple, who assisted in the work 
 for the Boston Water Works, has sug- 
 gested that this unit be made definite for 
 all persons, by taking it a fixed number of 
 square microns ; and for this purpose 20 
 
 FIG. 2. SECTION OF OPEN CELL, SHOWING CURVE OF 
 SURFACE OF FLUID DUE TO CAPILLARY ATTRAC- 
 TION AT SIDES. 
 
 seems to be the desirable unit. By care- 
 ful comparison with a stage micrometer 
 for a few times this unit can be firmly 
 fixed in mind, and an estimate of the 
 amount of amorphous matter made with 
 considerable precision. 
 
 The advantage of a cell of such depth 
 as to just contain the quantity taken for 
 examination is illustrated by Fig. 2, 
 which represents the open cell, and shows 
 the meniscus form taken by the liquid, by 
 reason of capillary attraction at the sides. 
 This curvature is so considerable as to 
 render a count in the squares near the 
 
74 
 
 edges of the cell impracticable, for optical 
 reasons, which every user of the micro- 
 scope will readily understand. With the 
 covered cell, on the contrary, the count may 
 be made up to the sides as easily and with 
 -as much certainty as in the middle. 
 
 The placing of the cover-glass is easily 
 accomplished, although the careful observ- 
 ance of certain details are essential to 
 uniform success. Thus, the cover-glass 
 should be perfectly clean, and just before 
 placing should be moistened. The opera- 
 tion of putting it to place consists in lay- 
 ing one end, held in a horizontal position, 
 in contact with the ground upper surface 
 of the metallic portion of the cell, and, 
 while keeping it in close contact at all. 
 points, gradually sliding it forward until 
 the whole ce.ll is covered. 
 
 In this connection it may be noted that 
 cleanliness is quite essential in all these 
 operations ; and the hints given by Dr. 
 XfacDonald in his Water Analysis fully 
 cover the .case. 
 
 In the original cell, as designed by 
 Prof. Sedgwick, the division into squares, 
 
75 
 
 for the purpose of obtaining the rela- 
 tion of organisms to area, was arrived 
 at, as already stated, by ruling square mil- 
 limetres upon the upper surface of the 
 glass slide on which the cell is based. 
 This, however, gives a unit square only 
 for the bottom of the cell ; and for all 
 organisms at the top of the liquid no unit 
 of area is obtained; inasmuch as the con- 
 siderable change of focus required in order 
 to see them at all, renders it impossible to 
 distinguish the ruled lines and such float- 
 ing objects at the same time. AVith the 
 eye-piece micrometer, however, this diffi- 
 culty is removed, and the unit square is 
 clearly in the field of vision without ref- 
 erence to the plane in the cell upon which 
 the objective is focused. 
 
 The working objective for these counts 
 may be either a two-thirds or one-half 
 inch ; and for identification of minute un- 
 known forms, a one-fourth or one-fifth 
 water immersion capable of working 
 through a thick cover-glass, and cell one 
 millimetre in depth, would be useful. I 
 have, however, no experience with a high- 
 
76 
 
 power objective of this character, and can 
 only cite the opinion of the Rochester 
 opticians that such an objective of satis- 
 factory correction and definition can be 
 made. 
 
 In this connection it may be mentioned 
 that Mr. E. Gundlach has made, at the 
 author's request, a dry fourth which pos- 
 sesses the necessary working distance, and 
 is, therefore, easily used to determine 
 objects at the very bottom of the cell, 
 even when a thick cover-glass is in place. 
 Such an objective is, however, doing its 
 work through three mediums, all varying 
 in refractive index ; namely, air, glass, and 
 water, and, as may be easily predicated, 
 the trial objective is not entirely a success. 
 The angle is, of course, very narrow, though 
 this defect is inseparable from long work- 
 ing distance. The greatest difficulty is 
 the imperfection in the correction of the 
 chromatic aberrations. It is improve- 
 ment in this direction which is chiefly 
 expected to result from the use of a water 
 immersion. The dry objective is, however, 
 of considerable use in assisting in de- 
 
77 
 
 termining very minute objects which 
 present only a simple structure ; it fails 
 utterly when those requiring any resolv- 
 ing power are encountered. 
 
 The following table shows the compara- 
 tive value of the open cell with mixed 
 sand and organisms, and the covered cell 
 with sand and organisms separated. The 
 results are in number of organisms per 
 cubic centimetre, and represent only the 
 plant forms present in the given samples. 
 
 
 
 
 ) 
 
 (2 
 
 ) 
 
 ORGANISMS. 
 
 Open 
 
 Closed 
 
 Open 
 
 Closed 
 
 
 cell with 
 
 cell with- 
 
 cell with 
 
 cell with- 
 
 
 sand. 
 
 out sand. 
 
 sand. 
 
 out sand. 
 
 Asterionella 
 
 14 
 
 30 
 
 7 
 
 23 
 
 Tabellaria . 
 
 11 
 
 21 
 
 4 
 
 15 
 
 Cyclotella . 
 
 1 
 
 1 
 
 
 
 2 
 
 Anabaena . 
 
 2 
 
 16 
 
 7 
 
 13 
 
 Clathrocystis 
 Coelosphaerium 
 
 4 
 5 
 
 6 
 12 
 
 1 
 5 
 
 8 
 3 
 
 Nostoc . . 
 
 
 
 2 
 
 1 
 
 1 
 
 Melosira . . 
 
 2 
 
 20 
 
 1 
 
 1 
 
 Totals . . . 
 
 39 
 
 108 
 
 26 
 
 66 
 
 A number of similar comparative counts 
 have been made, with the result of uni- 
 
78 
 
 formly getting a larger number of or- 
 ganisms by the Sedgwiek-Rafter method. 
 
 In the recently published Twenty- 
 Second Annual Report of the Massachu- 
 setts Board, it is stated as the result of the 
 various comparisons made by the biolo- 
 gists of that Board, that the improvement 
 in processes has resulted not only in an 
 increase in the total number of organisms 
 found in a given water, but also in the 
 number of genera. Thus, in a general way, 
 the number of organisms observed by 
 Prof. Sedgwick's original sand method is 
 several times that observed by the cloth 
 method of Mr. Parker; likewise the number 
 observed by the Sedgwiek-Rafter method 
 is probably from two to four times the 
 number observed by the sand method. 
 
 The foregoing indicates rather briefly 
 the several steps taken by different 
 workers before we could be said to have a 
 practicable method of making the micro- 
 scopical examination and enumeration 
 of the living organisms in potable water, 
 which fairly met all the conditions. 
 
 The author hopes that some worker of 
 
79 
 
 the immediate future will be able to still 
 further advance the method along the road 
 to ultimate perfection. 
 
 VALUE OF METHOD. 
 
 The value of a method of this character 
 will be readily recognized by all who un- 
 derstand the limitations of chemical analy- 
 sis, as applied to the decision of questions 
 relating to the sanitary value of potable 
 water. The most useful of the various 
 chemical methods recognizes in effect only 
 two classes of organic impurity ; namely, 
 free and albuminoid ammonia ; and groups 
 every organic substance occurring in water' 
 as one or the other of these. This has re- 
 sulted in the condemning of the waters of 
 mountain streams by chemists, who ven- 
 tured positive opinions as to sanitary value 
 on the evidence of chemical analysis alone. 
 The use of the biological method, by exhib- 
 iting clearly the character of the organic 
 contamination, will, therefore, lead to a 
 more accurate knowledge of potable waters 
 than can be gained by chemical analysis. 
 
 Moreover, as we gain more knowledge of 
 
80 
 
 the real sanitary significance of the various 
 forms of plant and animal life, the daily 
 or weekly fluctuations in quality of a public 
 water supply can be quickly obtained by 
 the use of this method of biological analy- 
 sis ; and it is probable that, in future, public 
 water supplies will be regularly subject to 
 such examinations. 
 
 RESULTS. 
 
 The following table shows a number of 
 counts of samples from different localities, 
 and illustrates the variations in number 
 
 NO OF 
 
 SAMPLE. 
 
 (1) 
 
 (2) 
 
 (3) 
 
 <*) 
 
 (5) 
 
 (6) 
 
 (7) 
 
 (8) 
 
 (9) 
 
 (10) 
 
 Sponge Spicules 
 Rhizopods . . 
 Infusoria . 
 Rotifera . . . 
 Crustacea . 
 
 1 
 
 5 
 1 
 
 
 1 
 2 
 2 
 1 
 
 
 
 
 6 
 
 
 
 
 
 80 
 
 
 
 
 
 21 
 3 
 
 
 1 
 1 
 50 
 6 
 1 
 
 1 
 
 16 
 
 1 
 
 
 
 1 
 
 
 
 
 3 
 1 
 
 10 
 2 
 
 
 
 
 
 11 
 
 3 
 
 
 Total Animals . 
 
 7 
 
 6 
 
 6 
 
 80 
 
 24- 
 
 59 
 
 18 
 
 1 
 
 16 
 
 14 
 
 Desmidieae . . 
 Diatomaceae 
 Zoospores . . 
 Chlorophyceae 
 Cyanophyceae . 
 Fungi . . . 
 
 
 50 
 130 
 2 
 15 
 3 
 
 1 
 6 
 51 
 
 5 
 38 
 
 1 
 
 1 
 12 
 73 
 4 
 70 
 
 
 
 
 o 
 
 280 
 1 
 4 
 
 
 3 
 19 
 244 
 55 
 157 
 
 
 4 
 45 
 88 
 13 
 110 
 
 
 5 
 50 
 2400 
 1 
 
 
 
 
 8 
 26 
 
 
 
 
 1 
 
 17 
 132 
 
 1 
 
 
 1 
 
 1 
 35 
 90 
 5 
 
 10 
 
 2 
 
 Total Plants . 
 
 200 
 
 102 
 
 160 
 
 287 
 
 478 
 
 260 
 
 2456 
 
 34 
 
 152 
 
 143 
 
 Amorphous 
 Matter . . . 
 
 80 
 
 75 
 
 140 
 
 180 
 
 238 
 
 230 
 
 45 
 
 165 
 
 170 
 
 240 
 
81 
 
 and kind of organisms found in various 
 waters. In this table the results are 
 grouped in classes to save space, and are 
 the number of organisms per cubic centi- 
 metre, as before. 
 
 In these samples (8) is from a spring, 
 and represents very pure water. All of 
 the samples except (5), (6), and (7) are 
 from water supplies, and represent water 
 of medium quality. The large amount of 
 Cyanophyceaein (5) and (6) might, of itself, 
 in the present state of our knowledge, lead 
 to the rejection of those two waters as 
 unfit for domestic purposes, especially if 
 continuous observation, extending over 
 two or more seasons, showed that such 
 extensive growths occurred frequently. In 
 all such cases, however, a study of the 
 environment would be desirable before 
 making a final decision, and it is not 
 intended to say positively that a given 
 sample can be definitely rejected on the 
 evidence of the microscopical examination 
 alone. The statement may, however, be 
 made that the microscopical examination 
 will, by itself, quite as frequently furnish 
 
82 
 
 definite evidence relative to the suitable- 
 ness or unsuitableness of a given sample 
 as can be obtained from a chemical examin- 
 ation alone ; while the microscopical exam- 
 ination in conjunction with a study of the 
 environment may easily furnish decisive 
 evidence for or against. This latter, state- 
 ment may be applied with equal force to 
 chemical examinations in conjunction with 
 studies of the environment ; and the con- 
 clusion is therefore reached, that in rational 
 water analysis, the microscopical examina- 
 tion stands on a par with the chemical. 
 This interesting and highly important con- 
 clusion has been fully recognized, as already 
 stated, by the chemists and biologists of 
 the Massachusetts Board, and we accord- 
 ingly find the two side by side in their 
 recent reports. The following tabulations 
 illustrate a typical series of such com- 
 pound analyses of water from Eeservoir 
 No. 4 of the Boston Sudbury Biver Supply, 
 extracted from the Twenty-Second Annual 
 Beport of that Board. Moreover, this par- 
 ticular series is of special interest by rea- 
 son of giving the results continuously, by 
 
83 
 
 months, for a year and a half; and the 
 movements of the plant and animal life in 
 conjunction with the variation in the am- 
 monias, as determined chemically, is clearly 
 shown, not only in a plane one foot below 
 the surface, but at mid-depth and near the 
 bottom. 
 
 In order to illustrate the question under 
 discussion fully, the series also includes 
 the examination of water from Cold Spring 
 Brook, the influent stream to Eeservoir 
 No. 4. 
 
84 
 
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 fi I'l 
 
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 1 1 1 1 1 1 1 1 1 
 
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 03 
 
 
 
 
 
 
 
 cc 
 
 
 
 Day of Examination 
 Number of sample 
 
 PLANT 
 Diatomacese 
 
 Ceratoneis 
 Melosira . 
 Navicula . 
 Nitzchia . 
 Synedra . 
 Tabellaria . 
 Algse (several genera) 
 Fungi. Crenothrix 
 
 ANIMAI 
 Rhizopoda. Actino 
 Infusoria . 
 Peridinium . ' . 
 Trachelornonas 
 
 TOTAL ORGANIS 
 
87 
 
 
 O 
 
 i 
 
 "1 
 
 8&*sas. 
 
 & 
 
 8 
 
 
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 C M 
 
 r-oo t jcocC'-i ^o 
 
 0000 
 
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 0000 
 
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 cog 
 
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 ss 
 
 g 
 
 00 
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 bC 
 
 10 1 
 
 55^, O'HO'-'CONCO 
 
 lH i^ 
 
 OH-O 
 
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100 
 
 DEDUCTIONS FROM THE OBSERVATIONS AT 
 RESERVOIR NO. 4. 
 
 A detailed study of the foregoing series 
 of chemical and microscopical analyses at 
 Reservoir No. 4 reveals a number of im- 
 portant points, the apparent significance of 
 which will be briefly pointed out. 
 
 Eeservoir No. 4, situated in the town of 
 Ashland, on Cold Spring Brook, is about 
 three-quarters of a mile in length, and 
 when filled to the ordinary flow-line, has a 
 depth near the dam of about forty-five feet. 
 It is nearly two thousand feet wide at the 
 dam, and preserves a width of perhaps 
 twelve hundred feet to near the upper end. 
 The construction was completed in 1885, 
 and the reservoir filled for the first time 
 in April, 1886. The bottom was thor- 
 oughly cleaned of all loam, stumps, and 
 vegetable matter, and the margins deepened 
 wherever the original marginal depth at 
 high water was less than eight feet. The 
 water-shed is 6.06 square miles area, with 
 few inhabitants, but is somewhat swampy. 
 The storage capacity is about 1,100,000,000 
 
101 
 
 gallons when filled to the ordinary flow 
 level. 
 
 The foregoing series of analyses of water 
 from the Cold Spring Brook, are of samples 
 taken from the flowing stream a short 
 distance above the head of Reservoir 
 No. 4. 
 
 The samples from the reservoir itself 
 were taken at the depths indicated, from a 
 point about mid-way in the reservoir, not 
 far from the dam. ' 
 
 As stated in the report, the microscopi- 
 cal examinations from June, 1889, to 
 November, 1890, inclusive, were made by 
 Prof. Sedgwick's sand method; while 
 those for December, 1890, were made by 
 the Sedgwick-Rafter method. This may 
 be taken as partly accounting for the con- 
 siderable increase in the number of organ- 
 isms tabulated for the month of December, 
 1890, over that observed in November, and 
 the months immediately preceding. 
 
 While the results obtained are of great 
 interest, and strongly indicate the value of 
 the microscopical analysis in conjunction 
 with the chemical, it may nevertheless be 
 
102 
 
 observed that the work of the present 
 year will be likely to more decisively 
 exhibit such value ; not only by reason of 
 the improvement in method of examination, 
 but because of the increased experience of 
 the observers. The field of cryptogamic 
 botany and zoology necessary to be covered, 
 in order to make such examinations at all, 
 is large ; and the biologists who undertook 
 to make these studies were literally explor- 
 ing an unknown world. That their work 
 gives very satisfactory results at this early 
 date, can only be taken as the highest pos- 
 sible evidence of their painstaking in- 
 dustry. The work itself is the best 
 exposition of the new views, and it is 
 unnecessary to consume any large amount 
 of space in pointing out the details. A 
 few deductions may, however, be briefly 
 noted : 
 
 The running water of Cold Spring Brook 
 contained a number of species of Diatom- 
 acese \_Navicula, Nitzckia, Synedra], which 
 are either not found at the lower end of 
 the reservoir at all, or in much smaller 
 number. Of these, Navicula and Nitzchia 
 
103 
 
 are apparently entirely absent from the 
 reservoir, while Synedra, except at the bot- 
 tom, is present only in smaller quantity. 
 Thus in Cold Spring Brook the average 
 number per month of Synedra, per cubic 
 centimetre, for the twelve months of 1890, 
 is found to be 8.8. At a depth of one foot 
 below the surface in Reservoir No. 4, the 
 average number per month of Synedra for 
 the same period is 5.6. At mid-depth we 
 find 4.0, and near the bottom 9.0, Synedras 
 per cubic centimetre. 
 
 Collating the showing for Cydotella in 
 the same way, we find the form entirely 
 absent from the Cold Spring Brook. In 
 the reservoir this form is present at all 
 depths, only in the months of June, July, 
 and August ; 1890, the average per cubic 
 centimetre per month for the three months 
 being, at one foot below the surface, 49.0, 
 at twenty feet, 127.0, and at the bottom 
 18.0. 
 
 Taking the whole number of Diatomacece 
 the average per cubic centimetre per month 
 in Cold Spring Brook is 17.0 ; at one 
 foot below the surface in the reservoir, 
 
104 
 
 22.4; at twenty feet, 42.5; and near bot- 
 tom, 20.0. 
 
 Taking the total number of plant forms 
 and tabulating, we make the following 
 showing : 
 
 
 
 
 
 _; 
 
 
 aJ 
 
 
 
 
 
 
 
 o5 
 
 LOCALITY. 
 
 
 * 
 
 ,0 
 
 1 
 
 a 
 
 1 
 
 
 E 
 
 fc 
 
 37 
 
 ! 
 
 
 
 
 
 I 
 
 2 
 
 Cold Spring Brook 
 Reservoir No. 4, 1 
 
 3 
 
 5 
 
 
 
 9 
 
 34 
 
 76 
 
 60 
 
 131 
 
 15 
 
 6 
 
 ,7 
 
 76 
 
 35.7 
 
 foot below surface 
 
 31 
 
 2 
 
 15 
 
 13 
 
 130 
 
 215 
 
 20 
 
 44 
 
 29 
 
 11 
 
 14 
 
 152 
 
 56.3 
 
 Reservoir No. 4, 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 mid-depth . . 
 Reservoir No. 4, 
 
 25 
 
 3 
 
 
 
 9 
 
 55 
 
 129 
 
 278 
 
 27 
 
 
 
 6 
 
 6 
 
 195 
 
 61.1 
 
 near bottom . . 
 
 29 
 
 4 
 
 58 
 
 4 
 
 32 
 
 32 
 
 28 
 
 22 
 
 5 
 
 6 
 
 15 
 
 167 
 
 33.5 
 
 From this table it is clearly apparent 
 that the greatest activity of the micro- 
 scopical plants is in the months correspond- 
 ing to the highest temperature. December 
 we may leave out of this comparison, as by 
 reason of the increased number due to the 
 change in method, the record for that month 
 is probably abnormal so far as the balance of 
 the series is cpncerned. February appears 
 as a period of minimum plant life, while 
 October and November are also low. This 
 is as might be expected in February, though 
 
105 
 
 the record here gives a different result in 
 October and November from the author's 
 experience with other bodies of water in 
 which the microscopical plant life has been 
 found especially vigorous in these months. 
 The explanation must be looked for in 
 further study of samples from Eeservoir 
 No. 4, though a partial explanation may 
 be inferred by studying the relations of 
 the chemical constituents to the crypto- 
 gamic growths. Such relations can be 
 more conveniently shown by diagrams than 
 by either tabulations, or written descrip- 
 tions ; and Plates I. to IV. have accordingly 
 been prepared for this purpose. Studying 
 them, it appears that in Cold Spring Brook, 
 and also in the reservoir, at both surface 
 and mid-depth, the period of greatest devel- 
 opment of plant life bears a clear relation 
 to the maximum point reached by the 
 nitrates ; the same may also be affirmed of 
 the results of the examinations of samples 
 near the bottom, though probably some- 
 what different forces are at work near the 
 bottom of a deep body of water from those 
 either near the surface or at mid-depth, 
 
106 
 
 and points between. The nature of these 
 forces may be now indicated : 
 
 EFFECT OF LIGHT. 
 
 The chlorophylaceous and amylaceous 
 plants require light as the primary condi- 
 tion of growth ; and if we assume, for the 
 time being, a fixed condition of the water 
 at various planes, we may say that the 
 varieties of cryptogamic plant life, which 
 depend upon light, will decrease as we go 
 deeper in any given body of water, in 
 accordance with some law bearing a rela- 
 tion to the intensity of light at the given 
 plane. Changes in quality of light as 
 depth increases may result from two causes, 
 or, rather, from a combination of two causes. 
 There will always be either an increased 
 opacity of the water itself, due to increase 
 of coloring matter as the depth increases ; 
 or where the coloring matter is constant at 
 all depths, the decrease in intensity of 
 light will be in accordance with the general 
 law, that intensity decreases geometrically 
 as distance increases arithmetically. By 
 way of illustration, we may assume the 
 
107 
 
 opacity of a given body of water to be such 
 as to cut off ^ f fcne tota l intensity of light 
 at the depth of one foot. We have then, 
 after passing through one foot of such 
 water, Jg- of the original intensity at the 
 surface. In passing through the second foot, 
 the light again loses ^ of the total quantity 
 of light entering the second foot, or $ of 
 Jg. At the depth of two feet, the total 
 intensity is therefore |J of the original 
 intensity, and so on for any depth whatever. 
 On examining the color column in the 
 tables of results, or the profile of the same 
 on the diagrams, we find that great varia- 
 tions in color occurred in the water of Cold 
 Spring Brook, the color determinations run- 
 ning all the way from 3.50 in August, 1889, 
 to 0.30 in August, 1890. Also, that in 
 June, 1890, the color scale stands 1.80. 
 This of itself represents an enormous dif- 
 ference in the plant-producing capacity of 
 the water of this stream between June and 
 August, 1890, and by itself affords a partial 
 explanation of why the plant development 
 in August, 1890, was so greatly in excess 
 of that in June. Partial explanation is 
 
. 108 
 
 stated in the foregoing, because many 
 other circumstances tend to modify the 
 results, and no one cause can be assigned 
 as a full explanation. 
 
 If we consider the color scale in the 
 results for Beservoir No. 4, one foot below 
 the surface, we find that the range in vari- 
 ation in 1890 was from 0.35 in August and 
 September, to 0.85 in November; 0.50 
 being the figure for July and August in 
 that year. At mid-depth the figures for 
 1890 show 0.60 for June ; 0.50 for July ; 
 0.40 for August and September; 0.45 for 
 October; and 0.85 for November. Near 
 the bottom they are 0.70 for May and June ; 
 0.40 for July ; 0.35 for August ; 0.50 for 
 September ; 0.55 for October ; and 0.85 for 
 November. The relation of these to the 
 other results are also clearly indicated on 
 the diagrams. 
 
 Examining the tabulations further, it 
 appears* while a considerable number of 
 chlorophylaceous algae (Chlorophyceae) are 
 found at mid-depth, ' the number is still 
 much less than at one foot below the sur- 
 face; and near the bottom, the numbers 
 
109 
 
 run generally even smaller. This is as 
 may be predicated from what is -known in 
 reference to the influence of light on vege- 
 tation. In white light the rays of different 
 intensity of wave motion are commingled 
 in such manner that the various-colored 
 bands of the spectrum are not apparent. 
 Such light is normal so far as related to 
 physiological action on the processes of 
 vegetation. The chemical changes in grow- 
 ing plants, however, are chiefly due to the 
 rays of inferior wave motion.; as, for in- 
 stance, the red, orange, yellow, or green. 
 The mechanical changes, on the other hand, 
 are produced by the rays of high-wave 
 motion,; the blue, violet, or ultra-violet. 
 The former are chiefly concerned in the 
 production of chlorophyl, the decomposi- 
 tion of carbon dioxide, and the formation 
 of starch. The latter influence the rapid- 
 ity of growth, alter the movements of 
 protoplasm, compel swarm-spores to adopt 
 a definite direction in their motion, change 
 the tension of the tissues of the motile 
 organs, and hence affect their position, etc.* 
 
 * Sachs' Botany, p. 778. 32 
 
110 
 
 Again, the action of light on plants is in 
 proportion to its intensity. This question 
 is one with more than theoretical interest, 
 as is sufficiently shown by considering that 
 the production of starch in the chlorophy- 
 laeeous algae is dependent upon the quan- 
 tity of light which the plants receive. All 
 the free-floating forms are from a variety 
 of causes ; as, for instance, changes of tem- 
 perature, cessation of the production of gas 
 by the plants themselves, etc. ; quite sus- 
 ceptible to changes in specific gravity, and, 
 therefore, at different times, occupy differ- 
 ent levels in the water. In light of less 
 than a certain degree of intensity the 
 starch is not formed; the protoplasmic 
 matter, which, with sufficient intensity of 
 light, would go to the production of starch, 
 remains protoplasmic. Again, if algae, in 
 which starch is fully formed, are placed in 
 the dark, or in light of less than the starch- 
 producing degree of intensity, the starch 
 already formed will disappear; such changes 
 taking place as restore the starch material 
 to its original state. On being again 
 brought into strong light, the starch will 
 
Ill 
 
 reform, and by treatment in a suitable cul- 
 ture-cell, all these formations can, under 
 proper gradation of light, be observed for 
 a considerable length of time. 
 
 The application to be made of these 
 observations is in relation to the changes 
 in intensity of the light which will exist 
 at different depths in any given body of 
 water, and, consequently, in relation to the 
 varying quality of the water itself at dif- 
 ferent depths. In this connection it is- 
 important to clearly understand that the 
 production of chlorophyl and starch is very 
 intimately related to the chemical compo- 
 sition of water, and that if such conditions 
 obtain as preclude the continuance of their 
 formation, changes in chemical composition 
 may be expected to result. 
 
 This phase of the subject could be pur- 
 sued indefinitely, but the limits of a vol- 
 ume of the Science Series clearly will not 
 permit. The foregoing is a skeleton merely ; 
 and the reader who cares to pursue the 
 subject further must consult the great 
 works of Sachs'. 32aandb 
 
112 
 
 EFFECT OF TEMPERATURE. 
 
 The most important law of temperature 
 in relation to plant life with which we are 
 concerned, in an investigation of the 
 relation of cryptogamic growths to the 
 purity of a natural water, is that affirm- 
 ing, that in plant growth the exercise of 
 every function is restricted to certain 
 definite limits of temperature, within 
 which it alone can take place.* 
 
 A corollary to the foregoing may be 
 stated as follows : the functions of a plant 
 are assisted and accelerated in their in- 
 tensity when the temperature rises above 
 the lower limit for that function ; on 
 reaching a definite higher degree, a maxi- 
 mum of intensity is attained, the activity 
 then decreases with a further increase of 
 temperature, until it entirely ceases at 
 the upper limit.! 
 
 As a brief deduction from the foregoing 
 law, it may be assumed that some plants 
 (and the assumption is apparently en- 
 tirely true as applied to cryptogams) will 
 
 * Sachs' Botany, p. 727. t LOG. cit., p. 729. 
 
grow best in low temperatures, others in 
 high temperatures, the latter being much 
 the more numerous in this latitude. Or- 
 dinarily, therefore, the lowering of the 
 temperature of a body of water, as winter 
 approaches, will be accompanied by a de- 
 crease in the amount and variety of micro- 
 scopical life. Exceptions to this rule may, 
 however, be expected by reason of certain 
 forms flourishing in a low temperature. 
 
 Again, in very large and deep bodies of 
 water it is necessary to go only a few feet 
 (50 to 80) below the surface before a level 
 is reached in which the temperature is 
 practically constant throughout the whole 
 year. In such a body the few observations 
 that have been thus far made, indicate an 
 abundant development of both plant and 4 
 animal life in winter. This is finely shown 
 by Mr. Vorce in his paper on Forms Ob- 
 served in Water of Lake Erie, 25 where are 
 figured and described in the first part, one 
 hundred and ninety-two species of plants 
 and animals, all observed between Dec. 25, 
 1880 and Jan. 22, 1881. A study of Lake 
 Erie water for several years by Mr. Vorce, 
 
114 
 
 indicated the appearance of certain forms 
 at about the same time every year. This 
 observation as to periodicity of forms has 
 been verified by the author in his studies 
 of the water of Hemlock Lake. 
 
 In smaller bodies of water, like Reservoir 
 No. 4 of the Boston supply, it is uncertain 
 that any such permanency and periodicity 
 of the winter forms are maintained. Addi- 
 tional study is necessary to elucidate this 
 point. 
 
 PHYSICAL CONDITION OF THE WATER. 
 
 From the preceding, it is evident that 
 in generalizing the results of these ex- 
 aminations, it must be borne in mind that 
 April, May, and June are months of 
 1 increasing temperature ; July, August, and 
 September months of maximum tempera- 
 ture ; October, November, and December 
 months of decreasing temperature ; and 
 January, February, and March the months 
 of minimum temperature. The general ef- 
 fect of these changes on the quantity and 
 quality of the microscopical life has been 
 already briefly indicated ; it now remains 
 
115 
 
 to point out an important series of changes 
 in the body of water itself, due to the 
 fluctuations of temperature. 
 
 In the first place, in summer the mean 
 temperature of shallow bodies of water 
 will generally be higher than that of 
 deeper ones; this temperature will be 
 more quickly reached in the months of 
 increase, and more quickly lost in the 
 months of decrease. In winter the shal- 
 low body will usually exhibit a some- 
 what lower temperature than the deeper 
 one. 
 
 Again, as cold weather approaches, in 
 the fall, the upper layers of a body of 
 water become cooler than the layers im- 
 mediately below ; and there accordingly 
 results, by reason of gravitation, a com- 
 plete vertical circulation, through the influ- 
 ence of which the relative positions of the 
 top and bottom layers are reversed, down 
 to a depth where the temperature may be 
 expected to remain uniform for the whole 
 year. By way of illustrating the extent 
 of the force producing this overturning in 
 the fall, the following table of relative 
 
116 
 
 density and weight of a cubic foot of 
 water, at different temperatures, is in- 
 serted.* 
 
 
 1 Tempera- 
 ture. 
 
 Relative 
 Density. 
 
 ** 
 
 ^5 OT3 
 
 2fe 
 4s 2 
 
 m 
 
 
 
 
 
 
 32 
 
 .99987 
 
 62.416 
 
 
 
 
 
 
 35 
 
 .99996 
 
 62.421 
 
 
 
 
 
 
 39. 3 
 
 1. 
 
 62.424 
 
 
 
 
 
 
 45 
 
 .99992 
 
 62.419 
 
 
 
 
 
 
 50 
 
 .99975 
 
 62.408 
 
 
 
 
 
 
 55 
 
 .99946 
 
 62.390 
 
 
 
 
 
 
 60 
 
 .99907 
 
 62.366 
 
 
 
 
 
 
 65 
 
 .99859 
 
 62.336 
 
 
 
 
 
 
 70 
 
 .99802 
 
 62.300 
 
 
 
 
 
 
 75 
 
 .99739 
 
 62.261 
 
 
 
 
 
 
 80 
 
 .99669 
 
 62.217 
 
 
 
 
 
 July 4, 1889, Desmond FitzGerald, C. E., 
 and the author made a number of measure- 
 ments of the temperature of Lake Cochit- 
 uate, at a depth of sixty feet. A mean 
 of several of the observations gives a 
 
 * Smith's Hydraulics, p. 14. 
 

 117 
 
 temperature at that depth of 45. 4 ; the 
 change at points a short distance apart 
 being from 44.2 to 470. The surface 
 temperature at the point of making the 
 observations was 75.6, the air being 77. 2. 
 From the foregoing table, it appears that 
 a cubic foot of water at 45 weighs 
 62.419 pounds ; and at a temperature of 
 75 the weight is 62.261 pounds, giving a 
 difference at these temperatures of 0.158 
 pounds. 
 
 It is clear, therefore, that at this time of 
 year the bottom layers were certain to 
 remain at the bottom, by virtue of superior 
 gravity. On the approach of cold weather, 
 however, the decrease in temperature at 
 the surface increases the density there, 
 gradually leading to a complete vertical 
 circulation, as already indicated. 
 
 Again, in shallow bodies of water we may 
 further occasionally have a vertical circu- 
 lation, from bottom to top, due to the 
 influence of heavy winds ; and the upper 
 layers of a large and deep body may also 
 be expected to respond to the same source 
 of discrepancy. 
 
118 
 
 All these various modifying influences 
 must be taken into account in studying the 
 results of water-supply examinations. 
 
 LUDLOW RESERVOIR, SPRINGFIELD. 
 
 The main source of supply to the city of 
 Springfield, Massachusetts, is derived from 
 the Ludlow Storage Reservoir. The 'area 
 when filled, is about 445 acres, and the 
 total content 1,992,000,000 gallons. The 
 reservoir was constructed about 1875, and 
 during every summer since, the water has 
 been unpleasantly affected with bad tastes 
 and odors. The greatest depth is about 
 twenty-four feet, with an average of nearly 
 fourteen feet. Of the area flowed by the 
 reservoir, two hundred and eighty-one acres 
 were covered with forest, a portion of 
 which was swampy land with peaty de- 
 posits, from six inches to four feet in depth. 
 The peaty areas are all at least twelve feet 
 below the flow-line, and many of them 
 sixteen feet below. All trunks of trees 
 and brush were burned, and stumps cut 
 low and charred. Nearly six and one-half 
 acres of the most objectionable portion of 
 
119 
 
 the swamp were sanded over to a depth 
 of about one and one-half feet. The shores 
 are mostly abrupt, the only exception be- 
 ing a small shallow area at the upper end. 
 
 The original plan included the uniting 
 of several water-sheds by canals ; and the 
 total tributary area was 6,484 acres. In 
 1886 a portion of this was cut off, leaving 
 at the present time 4,358 acres, on which 
 there is only a very small population.* 
 
 The chemical and microscopical analyses 
 recorded in the following tables are of the 
 greatest interest, as showing the relation 
 between the high ammonias and the ex- 
 cessive development of plant, and, at times, 
 of animal life. These" relations are so 
 clearly shown by the tables and diagrams 
 that an extended discussion may be omitted. 
 A few points only will be noted. In the 
 first place, the reader's attention is directed 
 to the fact, that during the whole time 
 covered by these tables, this -water has 
 been in constant use for domestic purposes 
 in the city of Springfield; the total con- 
 sumption for all purposes being about 
 4,000,000 gallons per day. 
 
 * Special Report, Tart I., pp. 296-7. 13 c 
 
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128 
 
 DEDUCTIONS FROM THE LUDLOW RESER- 
 VOIR DIAGRAM. 
 
 A study of the diagram of the results of 
 the chemical and microscopical examina- 
 tions, Plate V., of water from six feet 
 below the surface of Ludlow B/eservoir, 
 further elucidates a number of points of 
 interest in relation to the connection be- 
 tween the light transmitting capacity of 
 water, and the production of excessive 
 growths of microscopical plants and ani- 
 mals. One explanation of such growths 
 has been what may be termed the theory of 
 sufficiency of food ; according to which, it 
 is assumed that excessive developments of 
 any given organism can only occur in a 
 particular locality, when the kind of food 
 required by the organism is present in 
 that locality in sufficient abundance to 
 nourish the developing form. This theory, 
 while, as a general proposition essentially 
 true, is still, by reason of the existence of 
 a number of modifying elements, hardly 
 a full explanation of all the attending phe- 
 nomena, as may be briefly pointed out. 
 
129 
 
 The so-called free ammonia and the 
 mineral nitrates, are the two chemical 
 constituents which contribute most exten- 
 sively to the nourishment of minute plants 
 in potable water. Both of these are rela- 
 tively low in Ludlow Reservoir, for the 
 whole time covered by these observations. 
 If, however, we examine the relation of 
 the color line on the diagram to that of 
 the Diatomaceae, Chlorophyceae, Cyanophy- 
 ceae. and Infusoria, we discover that the 
 several maximum developments of micro- 
 scopical life have all occurred, either 
 when the color scale was decreasing, or at 
 or near a minimum. In no case during the 
 period from June, 1889, to December* 1890, 
 has there been an excessive development 
 of life while the color scale was high. 
 Again, a rise in the color scale has appar- 
 ently been followed, usually, by a decrease 
 in the number of organisms. Again, in 
 August, 1890, a rise of the Diatomaceae to 
 1,950 per cubic centimetre, was nearly co- 
 incident with a fall of the color scale from 
 0.50 to 0.15. If we examine other tabula- 
 tions of large developments of minute life, 
 
130 
 
 as given in the Report of the Massachu- 
 setts Board, we find a number of confir- 
 mations of the general law here indicated. 
 Some exceptions are also found, but the 
 evidence in favor is apparently somewhat 
 in excess of that against. 
 
 A study of the several tables, in refer- 
 ence to the point under discussion, indi- 
 cates, further, that the excessive growths 
 of microscopical life have usually, thus far, 
 occurred in Massachusetts in waters of 
 relatively low color scale ; a point which, 
 if found true on further study, must be set 
 down to the credit of the colored waters, 
 as indicating that they are somewhat less 
 liable to sudden deteriorations of taste 
 and odor than the colorless or so-called 
 white waters. The whole subject of plant 
 and animal development in potable waters 
 is, however, still in its infancy, and pro- 
 visional conclusions can only be drawn at 
 present. It is not intended, therefore, to 
 assert that the law of development of 
 minute forms in an inverse ratio to the 
 amount of color is yet fully proven. Its 
 demonstration, if made at all, will follow 
 
131 
 
 from further, and more accurate and elabo- 
 rate, tabulations of the amount of minute 
 life.' 
 
 The question may, however, be very 
 appropriately asked, why the theory of 
 sufficiency of food does not fully explain 
 the cause of the excessive development 
 which regularly takes place not only in the 
 Ludlow Reservoir, but in many other 
 similar bodies of water ? 
 
 A complete answer will lead to the con- 
 sideration of somewhat profound questions 
 in relation to the reproduction and devel- 
 opment of the Protophyta and the Pro- 
 tozoa,' and will indeed lead, figuratively, 
 into rather deep water. The question was, 
 however, ably discussed by Alexander 
 Braun, forty years ago, in his "Rejuven- 
 escence in Nature." " Braun takes up the 
 question more especially in its relation to 
 the life and development of plants, and 
 shows that among the cryptogams, at any 
 rate, there are alternating periods, on the 
 one hand, of moderate reproduction, and, 
 on the other, of extraordinary reproduc- 
 tion ; that during the first period, the life 
 
132 
 
 forces of the plant are gradually conserv- 
 ing themselves for the necessarily excess- 
 ive effort required in the second. There 
 is, therefore, an alternation of generations, 
 the respective periods of which are as yet 
 indeterminate ; and we may conclude that 
 the excessive development of minute life 
 which has characterized water-supplies 
 suffering from bad tastes and odors, is 
 merely a manifestation of one phase of 
 such alternation ; but why, in many cases, 
 occurring at irregular intervals, we are, as 
 yet, unable to definitely say. 
 
 An explanation of this irregularity of 
 appearance of these troubles may be found 
 in the case of some of the Cryptogams, in 
 the consideration that the spores, after a 
 period of activity, enter into a resting 
 state, and only re-awaken to a new life 
 after more or less complete desiccation 
 and resubjection to moisture. It is quite 
 possible, in this view, that many years 
 may intervene between periods of such 
 disturbances of a water supply by any 
 given cryptogam. 
 
 Returning for a moment to the subject 
 
133 
 
 of colored water, the statement can be now 
 made, that while a given colored water 
 may be the subject of an excessive devel- 
 opment of plant life, nevertheless, other 
 things being equal, the development would 
 be for many species more pronounced, 
 when once started, in either a colorless 
 water or one of low color scale, than in 
 waters of high, or relatively high, color 
 scale. The decrease in intensity, or the 
 modification in quality, of light, resulting 
 from the presence of the coloring matter 
 may be expected to exert a modifying in- 
 fluence on the activity of any given crypto- 
 gamic development. 
 
 In reference to the Ludlow Eeservoir it 
 may be said, by way of concluding the 
 subject, that the old, swampy bottom of 
 this reservoir must be considered as un- 
 favorable for maintaining a high degree of 
 freedom from cryptogamic growths. Such 
 a location may be expected to contain the 
 accumulated resting spores of various 
 Cryptogams for many years. The origi- 
 nal flooding of the reservoir started this 
 accumulation of resting spores into vigor- 
 
134 
 
 cms life ; the energy of the development 
 being possibly proportionate to length of 
 the period of rest. The original construc- 
 tion should, therefore, have included the 
 sanding of the entire bottom to the depth 
 of at least two feet, instead of the worst 
 portions to the depth of a foot and a half. 
 The existing conditions can probably be 
 improved by correcting the shallow flow- 
 age at the upper end, and keeping the 
 reservoir as nearly full as possible : we 
 thereby eliminate the opportunity which 
 now exists for an annual desiccation and 
 revivification of spores. Systematic obser- 
 vations of the kind, made in X 1889 and 
 1890, will be likely, then, to determine if 
 any marked decrease in number and vari- 
 ety of organisms is taking place, as may 
 be expected if the foregoing theory is 
 approximately true. It is, however, ex- 
 ceedingly doubtful if there will be any 
 marked improvement so long as the alter- 
 nate covering and uncovering of the shal- 
 low portions at the upper end furnishes 
 annually the ideal conditions for active 
 cryptogamic development. All that can 
 
135 
 
 be hoped for, with present conditions, is 
 that the generations of little plants and 
 animals may in time exhaust themselves : 
 as yet there is absolutely no data for pre- 
 dicting when this will take place. 
 
 The water supply of Brockton, Mass., 
 presents a case of a water in which the color 
 is usually high (the minimum from June, 
 1889, to December, 1890, is 0.45> the maxi- 
 mum 1.30, and the mean 0.85), and which 
 is also the source of an abundant crypto- 
 ganiic life. A comparison of the tabula- 
 tions indicates that here, also, the general 
 law of relation of the development of the 
 plants to intensity of light, as indicated 
 by the color scale, is found to fairly hold 
 good as shown in the case of Ludlow Res- 
 ervoir. 
 
 The foregoing is a skeleton of the new 
 art of the quantitative microscopical exam- 
 ination of potable water. The list of 
 literature will show the several sources of 
 useful information. 
 
LITERATURE. 
 
 THE following list of books, journals, 
 and miscellaneous papers does not in any 
 sense exhaust the several subjects. With 
 three or four exceptions it includes only 
 those either in the author's own collection, 
 or to which he has, at various times, had 
 access. A considerable number, both of 
 books and papers of little value for actual 
 work at the present time, have been 
 omitted ; and the list may, therefore, be 
 taken as including, so far as the author 
 can judge from his own experience, only 
 those likely to be of utility, either in 
 studying the sanitary relations and biology 
 of a public water supply and cognate ques- 
 tions, or in making the microscopical ex- 
 amination of potable water. Those who 
 desire a more complete bibliography are 
 referred to the volumes in the following 
 list, which are specially indicated by the 
 double asterisks thus,** where exhaust- 
 137 
 
138 
 
 ive lists of the several special subjects 
 may be found. The Natural History Cata- 
 logues of W. P. Collins, 157 Great Port- 
 land Street, London, W., may also be 
 profitably consulted for lists of books and 
 papers on the various forms of micro- 
 scopical life. 
 
 A very few books on the microscope 
 -are included in this list, to which the ob- 
 jection may be made, that they are of a 
 popular character rather than scientific. 
 To this objection it may be stated, that all 
 such which are included have been of use 
 to the author by furnishing some fact not 
 found elsewhere ; and it is with the ex- 
 pectation that they may be of similar use 
 to others that they appear here. 
 
 I. WATER IN ITS CHEMICAL, BIOLOGICAL, 
 AND SANITARY RELATIONS. 
 
 1. Blyth, A. W. : A Manual of Public 
 Health. 8vo, London, Macmillan & Co., 
 1890. 
 
 2. Buck, A. H. : A Treatise on Hygiene 
 and Public Health. 2 vols, 8vo, New 
 York, Wm. Wood & Co., 1879. 
 
139 
 
 3. Chambe.rlain, C. W. : Organic Impuri- 
 ties in Drinking Water. Paper in An. 
 Kept, of Conn. St. Bd. Health, 1883, pp. 
 259-280. 
 
 3^. Cohn, F. : Ueber den Brunnenfaden 
 (Crenothrix polyspora), mit Bemerkungen 
 iiber die Mikroscopische Analyse des Brun- 
 nenwassers. In Beitrage zur Biologie der 
 Pflanzen, 1870. 
 
 4. Davis, Floyd : An Elementary Hand- 
 book of Potable Water. 12 mo, Boston, 
 Silver, Burdett, & Co., 1891. 
 
 5. Drown, T. M. : (a) The Color and 
 Odor of Surface Waters. Jour. New Eng. 
 W. Wks. Assn., March, 1888. 
 
 (b) The Filtration of Natural Waters. 
 Jour. Assn. of Eng. Socs., 1890 ; also, Jour. 
 New Eng. W. Wks. Assn. Dec., 1890. 
 [For further on the same subjects, by 
 Dr. Drown, see Special Report' Mass. 
 Board, 1890, Part L] 
 
 6. Frankland, E. : Water Analysis for 
 Sanitary Purposes. 12mo, Philadelphia, 
 P. Blakiston, 1880. 
 
 7. Hassall, A. H. : (a) A Microscopic 
 Examination of the Water supplied to the 
 
140 
 
 Inhabitants of London and the Suburban 
 Districts. London, 1850. 
 
 (b) Food : Its Adulterations and the 
 Methods for their Detection. 12mo, 
 London, Longmans, Green, & Co., 1876. 
 
 8. Hirt, L. : Ueber den Principien und 
 die Methode der Mikroscopischen Unter- 
 suchung des Wassers. Zeitschrift fiir 
 Biologie, 1879. 
 
 8J. Hulwa, F. : Beitrage zur Schwem- 
 menkanalization und Wasser-Versorgung 
 der Stadt Breslau. Centralblatt ftir allge- 
 meine Gesundheitspflege, Erganzungshefte, 
 1885. 
 
 9. Kean, A. L. : A New Method for the 
 Microscopical Examination of Water. Sci- 
 ence, Feb. 15, 1889. Eng. News, March 
 30, 1889. 
 
 10. Leeds, A. R,. : Reports on the Water 
 Supply of Philadelphia. 
 
 (a) Eeport on the Condition of the 
 Schuylkill River in January, 1883. An. 
 Rept. Chf. Eng., Phil. W. Dept., 1883, pp. 
 343-372. 
 
 (6) Preliminary Eeport of a Chemical 
 Investigation into the Present and Pro- 
 
141 
 
 posed Future Water Supply of Philadel- 
 phia. An. Kept. Chf. Eng., Phil. W. 
 Dept., 1883. pp. 231-262. 
 
 (c) Eeport of Progress of a Chemical 
 Investigation, etc., W. Sup. of Philadelphia. 
 An. Kept. Chf. Eng., 1884, pp. 353-381. 
 
 (d) Final Eeport of a Chemical Investi- 
 gation, etc., W. Sup. of Philadelphia. An. 
 Kept. Chf. Eng., 1885, pp. 379-400. 
 
 11. Left'man and Bean : Examination 
 of Water for Sanitary and Technical Pur- 
 poses. 12mo, 'Philadelphia, P. Blakiston 
 .& Co.. 1889. 
 
 12. Mallet, J. W. : Eeports (1), (2), (3), 
 On the Eesults of an Investigation as to 
 the Chemical Methods for the Determina- 
 tion of Organic Matter in Potable Water. 
 An. Eept. Nat. Bd. Health for year ending 
 June 30, 1882, pp. 184-354. 
 
 13. Massachusetts State Board of 
 Health, Eeports. Boston, (a) On Some 
 Impurities of Drinking Water caused by 
 Vegetable Growths, by W. G. Farlow. 
 Supplement for 1879, pp. 131-152. 
 
 (b) Eeport of the Biologist, G. H. 
 Parker. Nineteenth An. Eept. 
 
142 
 
 (c) Special Report on Water Supply 
 and Sewerage, 1890. Part I. contains : 
 (1) The Chemical Examination of Waters 
 and the Interpretation of Analyses, by Dr. 
 T. M. Drown ; (2) Report upon the Organ- 
 isms, excepting the Bacteria, found in the 
 Waters of the State, by GL H. Parker; 
 (3) Summary of Water Supply Statistics, 
 by F. P. Stearns; (4) Classification of 
 Drinking Waters of the State ; (5) Special 
 Topics Relating to the Quality of Public 
 Water Supplies, by Messrs. F. P. Stearns 
 and Dr. T. M. Drown ; and (6) the Pollu- 
 tion and Self-Purification of Streams, by 
 F. P. Stearns. 
 
 Part II. contains : (1) A Report of the 
 Chemical Work of the Lawrence Experi- 
 ment Station, including Methods of Analy- 
 sis, and some Investigations of the Process 
 of Nitrification, by Messrs. Dr. T. M. Drown 
 and A. Hazen; (2) A Report of the Bio- 
 logical Work of the Lawrence Experiment 
 Station, including an account of Methods 
 Employed and Results Obtained in the 
 Microscopical and Bacteriological Investi- 
 gations of Sewage and Water, by Wm. T. 
 
143 
 
 Sedgwick; (3) Investigations upon Nitrifi- 
 cation and the Nitrifying Organism, by 
 E. 0. Jordan and Ellen H. Kichards. (In 
 addition, the general subject of water sup- 
 ply, its purification, and the purification of 
 sewage, are all treated exhaustively in this 
 Special Report.) 
 
 (d) Twenty-Second Annual Report con- 
 tains additional results of chemical and 
 microscopical examinations. 
 
 (e) Many of the earlier reports contain 
 much valuable matter, but the Nineteenth 
 to Twenty-Second Annuals, and the Special 
 Reports are the chief references for the 
 recent views. 
 
 14. MacDonald, J. D. : A Guide to the 
 Microscopical Examination of Drinking 
 Water. 2d ed., 8vo, London, J. and A. 
 Churchill, 1883. 
 
 15. Mills, H. : Micro-Organisms in Buf- 
 falo Water Supply and in Niagara River. 
 Proc. Am. Soc. Micrs., 1882. 
 
 16. Nichols, Win. Ripley : (a) On the 
 Filtration of Potable Water. Ninth An. 
 Rept. Mass. St. Bd. Health ; also reprint by 
 D. Van Nostrand, New York, 1879. 
 
144 
 
 () Eemarks on the Tastes and Odors of 
 Surface Waters. Jour. Assn. Eng. Socs., 
 Jan., 1882. 
 
 (c) Natural Filtration at Berlin. Jour. 
 Frank. Inst., CXIIL (1882), pp. 209-216. 
 (This paper contains an account of Creno- 
 tkrix, and a number of references to the 
 literature of that organism.**) 
 
 (d) Water Supply considered Mainly 
 from a Chemical and Sanitary Standpoint. 
 ** 8vo, New York, J. Wiley and Sous, 
 1883. 
 
 17. Parkes, E. A. : A Manual of Prac- 
 tical Hygiene. 2 vols. in 1, 8vo. From 
 last London ed., New York, Win. Wood 
 & Co., 1884. (Contains an appendix giving 
 the American practice.) 
 
 18. Parkes, L. C. : Hygiene and the 
 Public Health. 12mo, Philadelphia, P. 
 Blakiston, Son, & Co., 1889. 
 
 19. Radlkofer, L. : Mikroscopische Un- 
 tersuchung der Organischen Substanzen 
 im Brunnenwasser. Zeitschrift fur Biolo- 
 gie, 1865. 
 
 20. Rafter, G. W. : (a) On the Micro- 
 Organisms in Hemlock Water. Rochester, 
 1888. 
 
145 
 
 (b) On the Fresh-Water Algae and their 
 Relation to the Purity of Public Water 
 Supplies. Trans. Am. Soc. C. E., XXL 
 (1889), pp. 483-557. 
 
 (c) Biological Examination of Potable 
 Water. Prod. Roch. Acad. Sci., 1890, pp. 
 34-44. 
 
 (d) Deterioration of Water in Reser- 
 voirs; its Causes and Prevention. Four- 
 teenth An. Rept. Xew Jersey St. Bd. 
 Health, 1890, pp. 111-122. 
 
 21. Sedgwick, -Win. T. : (a) Recent Prog- 
 ress in Biological Water Analysis. Jour. 
 New Eng. W. Wks. Assn., Sept., 1889. pp. 
 50-55. 
 
 (b) Utilization of Surface Water for 
 Drinking Purposes. Jour. New Eng. W. 
 Wks. Assn., Sept., 1890, pp. 33-39. 
 
 (c) The Data of Filtration : Part I., Bac- 
 teria in Drinking Water. Part II., Oii 
 Crenothrix Kiihnina (Rabenhorst) Zopf, 
 Tech. Quart., Mass. Inst. Tech., 1890. 
 
 (d) Report as Biologist, in Special Rept. 
 Mass. Bd. (Noted under Mass. Repts.) 
 
 22. Smart, C. : Report on the Water 
 Supply of Mobile and New Orleans. Rept. 
 Nat. Bd. Health, 1880, pp. 441-514. 
 
146 
 
 23. Sorby, H. C. : Detection of Sewage 
 Contamination by the Use of the Micro- 
 scope and on the Purifying Action of Mi- 
 nute Animals and Plants. Jour. Soc. Arts, 
 XXXII. (1884), pp. 929-930 ; Jour. Eoy. 
 Micr. Soc., Ser. II., vol. iv. (1884), pp. 988- 
 991. 
 
 24. Tiemann and Gartner : Die Che- 
 inische und Mikroskopisch-Bakteriolo- 
 gische Untersuchung cles Wassers. 8vo, 
 Braunschweig, F. Viemeg and Son, 1889. 
 
 25. Vorce, C. M. : Microscopic Forms 
 Observed in Water of Lake Erie. Proc. 
 Am. Soc. Micrs. for the year 1881 and 
 1882. 
 
 26. Wanklyn, J. A. : Water Analysis. 
 12mo, 7th ed., !N"ew York, D. Van Nos- 
 trand Co., 1889. 
 
 27. Wilson, G. : A Handbook of Hy- 
 giene and Sanitary Science. 12mo, 5th 
 ed., Philadelphia, P. Blakiston, Son, & Co., 
 1885. 
 
 28. Wolff, A. J. : The Sanitary Exam- 
 ination of Drinking Water. Eighth An. 
 Kept. Conn. St. Bd. Health (1885), pp. 
 251-305. 
 
147 
 
 29. Zopf, W. : Entwickehmgsgeschlicht- 
 liche Untersuchung iiber Crenothrix Poly- 
 spora, die Ursache der Berlin Wassercala- 
 mitat. Berlin, 1879. 
 
 II. GENERAL BOTAXY. 
 
 30. Bessey, C. F. : Botany (Advanced 
 Course), 8vo, 5th ed., New York, Henry 
 Holt& Co., 1888.' 
 
 31. Gray, A. : Structural and Systematic 
 Botany and Vegetable Physiology. 8vo. 
 
 32. Sachs, J.: (a) Text-Book of Botany.** 
 Edited by Vines. 8vo, 2d ed., Oxford, 
 Clarendon Press, 1882. (b) Physiology of 
 Plants.** 8vo, Oxford, Clarendon Press, 
 1887. 
 
 III. CRYPTOGAMIC BOTAXY. 
 
 33. Bennett & Murray : A Handbook 
 of Cryptogamic Botany.** 12mo, New 
 York, Longmans, Green, & Co., 1889. 
 
 34. Grevilea : A Quarterly Eecord of 
 Cryptogamic Botany, 1872-1886. 
 
148 
 
 IV. FRESH-WATER 
 
 35. Cooke, M. C. : British Fresh- Water 
 Algae, exclusive of the Desmidiea? and 
 Diatomaceae.** 2 vols, 8vo, London, Wil- 
 liams & Norgate, 1882-1884 
 
 36. Hassali, A. H. : A History of the 
 British Fresh- Water Algae, including Des- 
 midieae and Diatomaceae. 2 vols, 8vo, 
 London. 1857. 
 
 37. Rabenhorst, L. : Flora Europaea Al- 
 garum Aquae Dulcis et Submarine.** 8vo, 
 Leipsic, 1864. 
 
 38. Wolle, F. : Fresh- Water Algae of 
 the United States.** 8vo, Bethlehem, 
 Pa., 1887. 
 
 39. Wood, H. C. : A Contribution to the 
 History of the Fresh-Water Algae of North 
 America.** 4to, Washington, 1872. 
 
 V. DESMIDIE.E. 
 
 40. Cooke, M. C. : British Desmids, a 
 supplement to British Fresh- Water Algae. 
 8vo, London, Williams & Norgate, 1886, 
 1887. 
 
 41. Ralfs, D. : The British Desmidiese. 
 8vo, London, 1848. 
 
149 
 
 42. Wolle, F.: Desmids of the United 
 States.** 8vo, Bethlehem, Pa., 1884. 
 
 VI. DIATOMACE^E. 
 
 43. Habirshaw, F. : Catalogue of the Dia- 
 tomacese. With references to the various 
 published descriptions and figures. New 
 York, 1877. 
 
 44. Smith, Win. : Synopsis of the Brit- 
 ish Diatomacese. 2 vols. 8vo, London, 
 1853-1856. 
 
 45. Smith, H. L. : A Contribution to the 
 Life History of the Diatomacese. Proc. 
 Am. Soc. Micrs., 1886, 1887. 
 
 46. Van Heurck. H. : Synopses des Di- 
 atomees de Belgique.** 2 vols. 8vo, An- 
 vers, 1885. 
 
 47. Wolle, F. : Diatomaceae of North 
 America.** 8vo, Bethlehem, Pa., 1890. 
 
 VII. FUNGI. 
 
 48. Cooke & Berkeley: Fungi: Their 
 Nature, Influence, and Uses. 3d ed., 12- 
 mo, London, Kegan, Paul, Trench, & Co., 
 1883. 
 
150 
 
 49. Crookshank, E. M. : Manual of Bac- 
 teriology.** 3d ed., 8vo, New York, D. 
 H. Vail & Co., 1891. 
 
 50. De Barry, A. : Comparative Mor- 
 phology and Biology of the Fungi, Myce- 
 tozoa, and Bacteria.** 8vo, Oxford, Clar- 
 endon Press, 1887. 
 
 51. Mathews & Lott : The Microscope 
 in the Brewery and Malt House. 8vo, 
 New York, I). Appleton & Co., 1889. 
 
 52. Pasteur, L. : Studies on Fermen- 
 tation. 8vo, London, Macmillan & Co., 
 1879. 
 
 53. Schiitzenberger, P. : On Fermenta- 
 tion. 12mo, New York, D. Appleton & 
 Co., 1889. 
 
 VIII. GENERAL ZOOLOGY. 
 
 54. Brooks, W. K. : Handbook Inverte- 
 brate Zoology. 8vo, Boston, 1882. 
 
 55. Clauss, C. : An Elementary Text- 
 Book of Zoology. 2 vols. 8vo, London, 
 Macmillan & Co., 1885. 
 
 5G. Huxley, T. H. : Manual of the Anat- 
 omy of Invertebrated Animals. 8vo, 
 1877. 
 
151 
 
 IX. MICROSCOPICAL CRUSTACEA. 
 
 57. Baird, W. : The Natural History of 
 the British Entomostraca.** 8vo, London, 
 Ray Society, 1850. 
 
 58. Herrick, C. L. : (a) Microscopic En- 
 tomostraca. An. Rept. of the Geolog. and 
 Nat. His. Sur. Minn., 1878, pp. 81-123 T 
 21 Plates. 
 
 (b) A Final Report on the Crustacea of 
 Minnesota, included in the Orders Cla- 
 docera and Copepoda.** Geol. and Nat. 
 His. Sur. Minn., 30 Plates, Minneapolis, 
 1884. 
 
 X. ROTIFERA. 
 
 59. Herrick, C. L. : Notes on American 
 Rotifera. Bull. Sci. Lab. Dennison Uni- 
 versity, pp. 43-62, Granville, Ohio, 1885. 
 
 60. Hudson and Gosse : The Rotiferru 
 or Wheel Animalcules, both British and 
 Foreign.** Roy. 8vo, 2 vols. with Sup- 
 plement, London, Longmans, Green, . & 
 Co., 1889. 
 
152 
 
 XI. POLYZOA. 
 
 61. Allman, G. J. : The Fresh-Water 
 Polyzoa.** Fol.. London, Ray Society, 1856. 
 
 02. Hyatt, A. : Observations on Poly- 
 zoa.** Proc. Essex Inst., IV. and V., 
 Salem, 1866-1868. 
 
 63. Stokes, A. C. : The Statoblasts of 
 our Polyzoa. The Microscope, IX., 1889. 
 
 XII. INFUSORIA. 
 
 64. Kent, W. S. : A Manual of the 
 Infusoria.** 2 vols.. Roy. 8vo, London, 
 David Bogue, 1880. 1881. 
 
 65. Pritchard, A. : A History of Infu- 
 soria, including the Desmidiaceae and Dia- 
 tom acese.** (Also includes the Rotifera.) 
 4th ed., 8vo, London, Whittaker & Co., 
 1861. 
 
 66. Stokes, A. C. : A Preliminary Con- 
 tribution towards a History of the Fresh- 
 Watea' Infusoria, of the United States. 
 Jour. Trenton Nat. His. Soc., I., 1888, 
 pp. 71-344. 13 Plates. 
 
153 
 
 XIII. RHIZOPODS. 
 
 67. Leidy, J. : Fresh-Water Rhizopods 
 of North America.** Published by U. S. 
 Geol. Sur., 4to, Washington, 1879. 
 
 XIV. SPONOIDJE. 
 
 68. Bowerbank, J. S. : (a) Monograph 
 of the Spongillidse.** Proc. Zool. Soc., 
 London, 1863. (b) On the British Spon- 
 giadae.** 3 vols., London, Eay Soc., 
 1864-1874. 
 
 69. Carter, J. S. : History and Classi- 
 fication of the Known Species of Spongil- 
 la.** Anns, and Mag. Nat. His., London, 
 1881. 
 
 70. Mills, H. : Fresh- Water Sponges. 
 Proc. Am. Soc. Micrs., 1882-1884-1888. 
 
 71. Potts, E. : Contributions towards a 
 Synopsis of the American Forms of Frebh- 
 Water Sponges, with Descriptions of those 
 named by other Authors, and from all pai-ts 
 of the World. Proc. Acad. Nat. Sci., Phila- 
 delphia, Pt. II., Apr.-Aug., 1887, pp. 15S- 
 279. 8 Plates. 
 
154 
 
 XV GENERAL PHYSICS. 
 
 72. Deschamel, A. P. : Elementary Trea- 
 tise on Natural Philosophy. 8v r o, New 
 York, D. Appleton & Co., 1875. 
 
 73. Ganot, A. : Traite Elementaire de 
 Physique. 12mo, Paris, 1868. 
 
 74. Jamin, M. J. : Cours de Physique de 
 PEcole Polytechnique. 4 vols., Paris, 
 1883. 
 
 XVI. LIGHT AND ITS RELATIONS. 
 
 75. Koscoe, H. E. : Spectrum Analysis. 
 4th ed., 8vo, London, Macmillan & Co., 
 1885. 
 
 76. Schellen. H. : Spectrum Analysis. 
 2d ed., 8vo, London, Longmans, Green, 
 & Co., 1885. 
 
 77. Tyndall, J. : On Light. 2d ed., 
 12mo, New York, D. Appleton & Co., 1883. 
 
 XVII. OPTICS. 
 
 78. Aedis, W. S. : An Elementary Trea- 
 tise on Geometrical Optics. 12mo, Cam- 
 bridge, Deighton, Bell & Co., 1888. 
 
155 
 
 79. Glazebrook, K. T. : Physical Optics. 
 12mo, New York, D. Appleton & Co., 
 1883. 
 
 80. Lardner, D. : Optics. 12mo, Lon- 
 don, Crosby, Lockwood. & Co., 1878. 
 
 81. Monckhoven, D. Van : Photographic 
 Optics. 12mo, London, E. Hardwicke, 
 1867. 
 
 82. Parkinson. S. : A Treatise on Optics. 
 4th ed.. 12mo, London, Macmillan & Co., 
 1884. 
 
 XVIII. THE MICROSCOPE AND MICROSCOP- 
 ICAL TECHNOLOGY. 
 
 83. Bausch. E. : Manipulation of the 
 Microscope. 16mo, Rochester. 1885. 
 
 84. Beale, L. S. : (a) How to work with 
 the Microscope.* * 5th ed., 8vo, Phila- 
 delphia, Lindsay & Blakiston, 1880. 
 
 (b) The Microscope in Medicine. 4th 
 ed., 8vo, Philadelphia, Lindsay & Blakis- 
 ton, 1878. 
 
 85. Behrens, J. W. : A Guide for the 
 Microscopical Investigation of Vegetable 
 Substances.* * 8vo, Boston, S. E. Casino 
 & Co., 1885. 
 
156 
 
 86. Carpenter, W. B. : The Microscope 
 and its Bevelations.* * 6th ed., 12mo, 
 London, J. and A. Churchill, 1881. 
 
 87. Cole, A. C. : Studies in Microscop- 
 ical Science. 2 vols., 8vo, London, Bail- 
 Here, Tindall, & Cox, 1883. 
 
 88. Davis & Mathews : The Prepara- 
 tion and Mounting of Microscopic Objects. 
 New York, G. P. Putnam's Sons, 1890. 
 
 89. Davis, G. E. : Practical Microscopy. 
 2d ed., 8vo, London, David Bogue, 1882. 
 
 90. Frey, H. : The Microscope and 
 .Microscopical Technology.* * 8v"o, New 
 York, Win. Wood & Co., 1880. 
 
 91. Gage, S. H. : (a) Notes on Micro- 
 scopical Methods. 8vo, Ithaca, N. Y., 
 Andrus & Church, 1886-7. 
 
 (b) Notes on Histological Methods.* * 
 8vo, Ithaca, N. Y., Andrus & Church, 
 1885-6. 
 
 92. Hogg, J. : The Microscope : Its 
 History, Construction, and Application. 
 12th ed., 12mo, London, G. Routledge & 
 Sons, 1887. 
 
 93. Journals. 
 
 (a) The Am. Jour. Microscopy, 1876- 
 1881. 
 
157 
 
 (b) The Am. Monthly Micr. Jour., 1880- 
 1891. 
 
 (c) Jour, de Micrographie, Paris, 1877- 
 1891. 
 
 (d) Jour. Hoy. Micr. Soc., London, 1878- 
 1891. 
 
 (e) Monthly Micr. Jour., London, 1869- 
 1877. 
 
 (/) The Microscope. 1881-1891. 
 
 (g) Quarterly Jour. Micr. Soc., London, 
 1853-1868. 
 
 (h.) Zeitschrift fiir Wissenschaftliche 
 Mikroskopie und fur Mikroskopische Tech- 
 nik. Braunschweig, 1885-1891. 
 
 94. Griffith and Henfrey : The Micro- 
 graphic Dictionary. 4th ed. Svo, London, 
 J. Van Voorst, 1883. 
 
 95. Naegeli & Schwendener : The Mi- 
 croscope in Theory and Practice. 8vo, 
 London, Swan, Sonnenschein, Lowry, & 
 Co., 1887. 
 
 96. Nave, J. : Collector's Handy-Book. 
 16mo, London, W. H. Allen & Co. 
 
 97. Queckett, J. : A Practical Treatise 
 on the Use of the Microscope. 3d ed., 
 8vo., London, H. Bailliere, 1855. 
 
158 
 
 98. Van Heurck, H. : Le Microscope, 
 sa construction, son maniement, et son 
 application speciale a Panatomie vegetale 
 et aux diatomees. 3d ed., Bruxelles, 1878. 
 
 XIX. MISCELLANEOUS, INCLUDING JOUR- 
 NALS OF BIOLOGY AND ZOOLOGY. 
 
 99. Braun, A. : Eejuvenescence in Na- 
 ture. 8vo, London. Ray Society, 1853. ; 
 
 100. Cooke, M. C. : (a) One Thousand 
 Objects for the Microscope. 16mo, Lon- 
 don. F. Warne & Co. 
 
 (Ij) Ponds and Ditches. 16mo, London, 
 1885. 
 
 (c) Rust, Smut, Mildew, and Mould : An 
 Introduction to the Study of the Micro- 
 scopic Fungi. 5th ed., 12ino, London, 
 W. H. Allen & Co., 1886. 
 
 101. Huxley and Martin : A Course of 
 Elementary Instruction in Practical Bi- 
 ology. 12m o, London, Macmillan & Co., 
 1883. 
 
 102. Journals of Biology and Zoology. 
 (a) American Naturalist. Salem and 
 
 Philadelphia, 1867-1891. 
 
159 
 
 (#) American Society of Microscopists, 
 Proceedings, 1879-1891. 
 
 (c) Archives de biologie, Paris, 1880- 
 1891. 
 
 (d) Archives de zoologie experimentale 
 et generale, Paris, 1883-1891. 
 
 (e) Mittheilungen aus der zoologischen. 
 Station zu Neapel, zugleich ein Keperto- 
 rium fiir Mittelmeerkunde. Leipsic, 1878, 
 1891. 
 
 (/) Zeitschrift fiir Biologic. Munich, 
 1865-1891. 
 
 103. Lankester, E. : Half-Hours with 
 the Microscope. 17th ed., 16mo, London, 
 W. H. Allen & Co., 1890. 
 
 104. Queckett, J. : Lectures on Histol- 
 ogy. (Elementary Tissues of Plants and 
 Animals.) 2 vols. 8\ r o, London, H. Bail- 
 Here, 1852. 
 
 105. Sachs, J. Von : History of Botany 
 (1530-1860). 12mo, Oxford, Clarendon 
 Press, 1890. 
 
 106. Sedgwick and Wilson : General 
 Biology, Part I. 8vo, New York, H. Holt 
 & Co., 1888. 
 
 107. Strasburger, E. : Microscopic Bot- 
 
160 
 
 any : A Manual of the Microscope in 
 
 Vegetable Histology. 8vo, Boston, S. E. 
 Casino, 1887. 
 
 108. Taylor, J. E. : The Aquarium. 
 Its Inhabitants, Structure, and Manage- 
 ment. London, W. H. Allen & Co., 1884. 
 
 109. Tyndall, J. : Essays on the Float- 
 ing Matter in the Air, in Relation to Putre- 
 faction and Infection. 8vo, ^"ew York, 
 D. Appleton & Co., 1884. 
 
 110. Wood, J. G. : Common Objects for 
 the Microscope. 16mo, London, G. Rout- 
 ledge & Sons. 
 
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