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Notices of Books. 
a reproduction of the inferior atom on a higher scale. Chemical 
combination consists in equal volumes of the different forms of 
matter coalescing and forming a new atomic molecule, and is 
therefore diredtly an affair of weight ; and the combining weights 
differ because the densities, atomic and molecular, differ. And 
he points out that liquefaction or solidification may not therefore 
involve the suppression of the atomic or molecular movement, 
but only the restriction of its range. 
All Mr. Graham’s results were obtained by the simplest possible 
means, and it is not a little remarkable thatthroughout the forty-six 
papers which the volume contains but few plates and woodcuts 
are necessary for their complete illustration. All his apparatus 
which could be found was exhibited at the Loan Collection of Appa- 
ratus held duringthe past year at South Kensington Museum, where 
it excited much interest from its simplicity as compared with the 
complicated appliances there gathered together. Some remarks 
which concluded a description of it may not be out of place here, 
for it taught that although in certain researches, or for accurate 
observation and measurement, delicate and complicated instru- 
ments may be necessary, the simplest appliances in the hands of 
a man of genius may yield the most important results. Thus 
with a glass tube and a plug of plaster-of-paris Mr. Graham dis- 
covered and verified the law of diffusion of gases. With a 
tobacco-pipe he proved indisputably that air is a mechanical 
mixture of its constituent gases. With a tambourine and a basin 
of water he divided bodies into crystalloids and colloids, and ob- 
tained rock crystal and red oxide of iron soluble in water. By 
the expansion of a palladium wire he did much to prove that hy- 
drogen is a white metal. And, finally, with a child’s india-rubber 
balloon filled with carbonic acid he separated oxygen from air, 
and established points the importance of which from a physio- 
logical point of view it is impossible to overrate. 
Dr. Smith has devoted 29 pages of the volume to a very accu- 
rate and valuable analysis of the papers, which he has in many 
cases collected from scientific periodicals now almost inaccessible 
even in this country. He has also added an excellent preface 
entitled “ Graham and Other Atomists,” which it may be well to 
quote at some length. 
“ Atoms and eternal motion are among the first-known scien- 
tific ideas. We find them discussed with full keenness by the 
earliest Greeks of whom we have received definite accounts.” 
Dr. Smith then states the views which have been held from the 
time of Leucippus, “ to whom the adtion of the atom as one sub- 
stance, taking various forms by combinations unlimited, was 
enough to account for all the phenomena of the world.” Graham 
took a similar view, and advanced the idea (of atomic motion 
with unity of material) to its utmost limit. The Greek told us 
all was motion ; Graham considered that the diversity in motion 
was only the basis of the diversity of the material, or, in other 
words, that an atom constituted an element of a special kind ac- 
