Sometimes, I filled a glass vessel with quicksilver, and introduced the air to it, when it was inverted in a bason of quicksilver. By this means I intirely avoided any mixture of common air; but then it was not easy to convey the gunpowder into it, in the exact quantity that was requisite for my purpose. This, however, was the only method by which I could contrive to fire gunpowder in acid or alkaline air, in which it exploded just as it did in nitrous or fixed air.
I burned a considerable quantity of gunpowder in an exhausted receiver (for it is well known that it will not explode in it) but the air I got from it was very inconsiderable, and in these circumstances was necessarily mixed with common air. A candle would not burn in it.
SECTION VIII.
Queries, Speculations, and Hints.
I begin to be apprehensive lest, after being considered as a dry experimenter, I should pass, with many of my readers, into the opposite character of a visionary theorist. A good deal of theory has been interspersed in the course of this work, but, not content with this, I am now entering upon a long section, which contains nothing else.
The conjectures that I have ventured to advance in the body of the work will, I hope, be found to be pretty well supported by facts; but the present section will, I acknowledge, contain many random thoughts. I have, however, thrown them together by themselves, that readers of less imagination, and who care not to advance beyond the regions of plain fact, may, if they please, proceed no farther, that their delicacy be not offended.
In extenuation of my offence, let it, however, be considered, that theory and experiment necessarily go hand in hand, every process being intended to ascertain some particular hypothesis, which, in fact, is only a conjecture concerning the circumstances or the cause of some natural operation; consequently that the boldest and most original experimenters are those, who, giving free scope to their imaginations, admit the combination of the most distant ideas; and that though many of these associations of ideas, will be wild and chimerical, yet that others will have the chance of giving rise to the greatest and most capital discoveries; such as very cautious, timid, sober, and slow-thinking people would never have come at.
Sir Isaac Newton himself, notwithstanding the great advantage which he derived from a habit of patient thinking, indulged bold and excentric thoughts, of which his Queries at the end of his book of Optics are a sufficient evidence. And a quick conception of distant analogies, which is the great key to unlock the secret of nature, is by no means incompatible with the spirit of perseverance, in investigations calculated to ascertain and pursue those analogies.