ADVERTISEMENTS About the EXPERIMENTS AND NOTES Relating to CHEMICAL Qualities.  
WHen, after I had gone through the common Operations of Chemistry, I began to make some serious Reflections on them, I thought 'twas pity, that Instruments that might prove so serviceable to the advancement of Natural Philosophy, should not be more studiously and skilfully made use of to so good a purpose. I saw indeed, that divers of the Chemists had by a diligent and laudable employment of their pains and industry, obtained divers Productions, and lighted on several Phaenomena considerable in their kind, and indeed more numerous, than, the narrowness and sterility of their Principles considered, could well be expected. But I observed too, that the generality of those that busy themselves about Chemical Operations; some because they practise Physic; and others because they either much wanted, or greedily coveted money, aimed in their Trials but at the Preparation of good Medicines for the humane body, or to discover the ways of curing the Diseases or Imperfections of Metals, without referring their Trials to the advancement of Natural Philosophy in general; of which most of the Alchemists seem to have been so incurious, that not only they did not institute Experiments for that purpose, but overlookt and despised those undesigned ones that occurred to them whilst they were prosecuting a preparation of a Medicine, or a Transmutation of Metals. The sense I had of this too general omission of the Chemists, tempted me sometimes to try, whether I could do any thing towards the repairing of it by handling Chemistry, not as a Physician or an Alchemist, but as a mere Naturalist, and so by applying Chemical Operations to Philosophical purposes. And in pursuance of these thoughts, I remember I drew up a Scheme of what I ventured to call a Chymia Philosophica, not out of any affectation of a splendid Title, but to intimate, that the Chemical Operations, there treated of, were not directed to the usual scopes of Physicians, or Transmuters of Metals, but partly to illustrate or confirm some Philosophical Theories by such Operations; and partly to explicate those Operations by the help of such Theories.  
But before I had made any great progress in the pursuit of this design, the fatal Pestilence that raged in London, and in many other parts of England, in the years 1664 and 65, obliging me among the rest to make several removes; which put me upon taking new measures, and engaging me in other employments of my time, made me so long neglect the Papers I had drawn up, that at last I knew not where to find them, (though I hope they are not yet mislaid beyond recovery,) which I was the less troubled at, because the great difficulties, to be met with in such an undertaking, did not a little discourage me, such a Task requiring as well as deserving a Person better furnished, than I had reason to think myself, with Abilities, Leisure, Chemical Experiments, and Conveniences, to try as many more as should appear needful. But yet to break the Ice for any that may hereafter think fit to set upon such a Work, or to shorten my own Labour, if I should see cause to resume it myself, I was content to throw in among my Notes about other Particular Qualities, some Experiments and Observations about some of those, that I have elsewhere called Chemical Qualities, because 'tis chiefly by the Operations of Chemists, that men have been induced to take special notice of them. Of these Notes I have assigned to some Qualities more, and to some fewer, as either the nature or importance of the Subject seemed to require, or my Leisure and other Circumstances would permit. And though I have not here handled the Subjects they belonged to, as if I intended such a Chymia Philosophica as I lately mentioned, because my design did not make it necessary, but did perhaps make it impertinent for me to do so, yet in some of the larger Notes about Volatility and Fixtness, and especially about Precipitation, I have given some little Specimens of the Theorical part of a Philosophical Account of those Qualities or Operations, that I hope will not be wholly useless. I know, it may be objected, that I should have employed for Instances some more considerable Experiments, if not Arcana; but though possibly I am not altogether unfurnished with such, yet aiming rather to promote Philosophy, than appear a Possessor of elaborate Processes, I declined several Experiments that required either more skill, or more time, or more expense than could be well expected from most Readers, and chose rather to employ such Experiments as may be more easily or cheaply tried, and, which is mainly to be considered, being more simple, are more clearly intelligible, and more fit to have Notions and Theories built upon them; especially considering, that the Doctrine of Qualities being itself conversant about some of the Rudimental parts, if I may so call them, of Natural Philosophy, it seemed unfit to employ intricate Experiments, and whose Causes were liable to many disputes, to settle a Theory of them. In short, my design being to hold a Taper not so much to Chemists as to the Naturalists, 'twas fit I should be less solicitous to gratify the former than to inform the later.  
FINIS.