i68 
Movement of Microscopic Particles 
[April, 
power from the water, and he acutely remarked that rocks 
generally undergo change when exposed to air and moisture. 
Bywater, indeed, was far from being the first who 
examined the motion of minute particles ; he was only the 
first who distinguished between the motions of living and 
dead particles. A series of physiologists — such as Buffon, 
Needham, Gleichen, Wrisberg, Muller, and Spallanzani — 
had been misled by these dancing particles into the belief 
that all bodies are formed of certain ultimate organic 
globules, which Spallanzani described as “ animaletti 
d’ultimo ordine.” Needham had, in 1749, published a 
quarto tra Ct called “ Observations upon the Generation of 
Animal Substances,” in which he described the motions of 
little eels and other small bodies. Buffon, who was ac- 
quainted with Needham, seems to have been thus led to 
start his celebrated theory of organical parts. He says* — 
“ God . . . has not only given form to the dust of the earth, 
but he has rendered it living and animated by enclosing in 
each individual a greater or less quantity of aCtive princi- 
ples, of organic living molecules, indestructible and common 
to all organised beings.” 
We may go back still further ; for in the “ Philosophical 
Transactions ” for 1696 (vol. xix., p. 280) is to be found a 
remarkable account of some microscopical observations 
by Stephen Gray, made by microscopes, or rather lenses, of 
very primitive construction ; yet Gray seems to have suc- 
ceeded in viewing these animated particles, and, considered 
by the light of later observations, the following passage is 
well worth quoting : — “ I have examined many transparent 
fluids, as water, wine, brandy, vinegar, beer, spittle, urine, 
&c., and do not remember to have found any of these with- 
out more or less of the bodies of these inseCts ; but I have 
not seen any in motion except in common water, that has 
stood for sometimes a longer, at others a shorter time, as 
has been observed by M. Leeuwenhoek ; though I do not 
remember he has observed that they are existent in the 
water before they revive. In the river, after the water has 
been thickened by rain, there are such infinite numbers of 
them that the water seems in great part to owe its opacity 
and whiteness to these globules. Rain-water, so soon as it 
falls, has many, and snow-water has more, of these globules.” 
It is probable that these moving globules were not really 
inseCts, but inorganic particles moving in the way we have 
* Histoire Naturelle, redige par Sonnini, tome xxiii., p. 2. See also 
tome xvii., ch. 6, p. 231. 
