STUDIES OF MATTER AND LIFE. 
155 
and of that size those only that are favourably placed. Mr. 
Sorby proceeded to inquire what sort of relation this power 
of microscopically assisted vision bears to the probable size of 
molecules of matter. He cited the results obtained by Stoney, 
Thompson, and Clerk-Maxwell, in attempts to calculate from 
different data the number of ultimate atoms in a given volume 
of any permanent and perfect gas at 0° C. and a pressure 
of one atmosphere. Thompson assigns as the greatest 
possible limit 98,320,000,000,000 in one-thousandth of 
an inch cube, which is of one cubic inch. Clerk- 
Maxwell, estimating the true number indicated by the pheno- 
mena of the interdiffusion of gases, made it 311,000,000; 
and Stoney, from his point of view, 1,901,000,000,000. The 
mean of these numbers is 50,260,000,000,000. In a letter 
received by the writer from Mr. Sorby, since the publication of 
his address in the “ Monthly Microscopical Journal ” for March, 
he assigns double weight to Clerk-Maxwell’s calculations, for 
reasons that we need not stop to explain, and considers the 
number of atoms in a cubic of an inch of gas to be about 
6,000,000,000,000, and that in the same space of liquid water 
the number of water atoms would be 3,700,000,000,000,000. 
V\ r ater is essential to organic life : if an organism is 
thoroughly deprived of it, death ensues, though some creatures 
may be dried so as not to exhibit the least appearance of 
moisture, then pass into a dormant state, and become active 
again when more water and an appropriate temperature are 
supplied. The common rotifer and the Anguillula britici have 
this property, and it is exhibited to some extent by that curious 
vertebrate, the Mud Fish, which survives an amount of 
drying that would be fatal to most animals as highly organised, 
though the baked mud in which it passes the hot dry season 
appears to prevent the desiccation from being carried too far for 
continuance of quiescent life. 
If we say water is so valuable to organic creatures on account 
of its dissolving so many substances they need to be supplied 
with in a fluid state, we may be asked why water has such 
power, and it seems probable that they depend upon the im- 
mense number of its molecules, as well as upon their mode 
of aggregation. Each atom or molecule in motion tends 
to set adjacent atoms or molecules in similar motion ; and a 
great number of small impulses, rhythmically repeated, easily 
set considerable masses of such bodies in fresh motions, differ- 
ing more or less from those which belong to their own constitu- 
tion. A child with a little hammer, tapping at a great log of 
wood, will in time set all the particles vibrating, and though 
each particle may move only through a small fraction of an 
