1878.] Microscopic Particles Suspended in Liquids. 
167 
II. ON THE MOVEMENT OF MICROSCOPIC 
PARTICLES SUSPENDED IN LIQUIDS. 
By Professor W. Stanley Jevons, LL.D., M.A., F.R.S. 
F we see a thing moving of its own accord, this sponta- 
neous motion is thought to be a sure sign that the 
objedt is an animal. Such an inference may be true 
of large bodies, but when we treat of microscopic objects 
the case is very different. Not only are minute vegetables, 
on the whole, as aCtive as animals, but even mineral parti- 
cles are found to be capable of moving as if endowed with 
life. This is a faCt which has been familiar to microscopists 
for half a century at least. The phenomenon was made 
widely known by the celebrated botanist, Robert Brown, of 
the British Museum, who, in the course of some observa- 
tions on the pollen of plants, discovered what he called 
active molecules , both in organic and inorganic bodies. He 
published his observations in two brief papers, which will 
be found in his “ Miscellaneous Works,” reprinted by the 
Ray Society (vol. i., p. 463). Considerable attention was 
drawn to the subject at the time, and the animated behaviour 
of particles became known as the Brownian movement % 
Brown, however, as he himself points out, was not 
the first discoverer of the phenomenon. A few years pre- 
viously John Bywater, a Liverpool man of some scientific 
merit, had published a traCt (in 1819), re-issued in 1824 
with additions, under the title “ Physiological Fragments ; 
to which are added Supplementary Observations to show 
that Vital and Chemical Energies are of the same Nature, 
and both derived from Solar Light.” The greater part of 
this book is occupied with vague and worthless speculations, 
but his observations are better. He found that “ small 
adtive linear bodies ” can be obtained from matter in general. 
That they could not be really animated he inferred from the 
fadt that they were yielded by coal just drawn from the pit, 
by the white ashes of coal, or by sandstone which had just 
been heated red-hot. Moreover, boiling kills animalcules, 
whereas he found that these lively particles could be boiled 
without suffering any loss of adtivity. Bywater came to the 
conclusion (p. 59) that these adtive bodies derive their vital 
