Using an improved microscope, Hooke again failed

Date: 
November 8, 1677

Using an improved microscope with better lighting and thinner pipes, Hooke again failed to demonstrate "Mr. Leewenhoeck's animals" in rainwater in which whole black pepper had steeped for two or three days. The members speculated about what the problem might be.

Birch's History, vol. 3, pp. 349, 351 notes:

The first thing exhibited was the experiment charged on Mr. Hooke at the last meeting, of examining pepper-water with better microscopes and thinner and small pipes. The fabric of the microscope for holding such pipes was new and more convenient and expeditious for such examinations than the usual forms, consisting wholly of pieces, which slid any ways very easily, and would stand fixed and steady in any posture, and admit light to the object every way: by the comparing of which various ways of inlightening the object one might the more easily and certianly discern the true shape and constitution of any body. But notwithstanding the pepper-mixture was very strong, being made of rainwater and whole black pepper steeped in it for two or three days; and notwithstanding the microscope was much better than that shown at the last meeting; yet nothing of Mr. Leewenhoeck's animals could be seen. Mr. Henshaw conjectured with a good deal of reason, that it was very likely, that it might not now be a proper season for their generations: and he was seconded by other observations, that the insects in water, from which gnats are bred, and such like, were observed to be generated only at certain seasons: and it was farther added, that a person, who had seen these animals in Holland the preceding summer with a microscope of his own, could not within a fortnight past find any such in pepperwater made here.

Dr. Whistler conjectured, that these small imagined creatures might indeed be nothing else than the small particles of the pepper swimming in the water, and no insects. But Dr. Mapletoft answered, that Mr. Leewenhoeck affirmed, that he had shewn them both alive and dead; dead, when he put vinegar to the pepperwater. However Mr HOOKE upon examining the said water in the pipe with a microscope found a vast quantity of small dust of pepper moving up and down in the water.

Mr. HOOKE suggested same farther improvement of that instrument by making use of the convexity of the surface of the liquor itself (put upon the plates of Muscovy glass) for augmenting the body within the liquor; as also for augmenting the body beyond it. The same might be done by small drops of fluids, that fall on the leaf of colewort or any oiled or greased surface; as also by the small drops at the end of small pipes, or sticking on small threads of glass or a single clue of silk, the said globular transparent bodies being viewed by the help of good microscopes.

Upon this occasion Mr. HOOKE mentioned again his way, which he had formerly acquainted the Society with, of making microscope-glasses with small drops of glass made by melting up the ends of threads in the flame of a candle into a globular figure, and then grinding all away upon a flat except a very small segment of the spherule; and so made use of as of a plane common glass, either for a single or compound microscope. He was desired to shew some specimen of this at the next meeting.

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