res. 
B.—CHEMISTRY. 37 
useful little manuals of the history of chemistry in particular, are hopeful 
signs. Our universities still lack a synthetic view of science as a whole, 
and there is little appearance of the general adoption of a philosophy of 
science which would bring about unity, but, if I may venture to express an 
opinion on such a controversial point, itis that scientific study and research, 
with its inevitable increasing subdivision, will become less satisfactory as 
a mental discipline unless connected by a broad synthetic survey of science 
as a whole. The older metaphysics having proved a broken reed, men of 
science here and there are building up a working philosophy of their own, 
and it is permissible to hope that investigators and philosophers together 
may, in due course, succeed in the construction of a synthesis in which the 
several sciences will be placed in due relation to one another, so that the 
minute field in which each investigator has of necessity to work will appear 
to him, not as a completely isolated region, but as a part of a great whole, 
the general outlines of which will be comprehended by every scientific 
worker. 
I trust that these criticisms will not be thought impertinent in one 
whose work lies in a specialised branch of applied chemistry, that of the 
common metals and their alloys, and I may now pass to the proper 
subject of this address, the chemistry of the solid state. It is remarkable 
how little we know with any certainty about the chemical properties of 
solids, although the idea of a solid is so fundamental. At the present 
time we always begin the study of chemistry with the gases on account 
of the simplicity of their mathematical treatment, but it must be 
remembered that this simplicity is the result of long study and of many 
discoveries. To the unscientific mind the solid is simpler, because more 
tangible. When men have tried to understand gases, they have expressed 
themselves in terms of solids. The atom, however attenuated it may 
have become in recent years, was in the first instance essentially a solid 
sphere, and the elasticity of gases has been explained in terms of the 
collision of elastic solid particles in motion. Newton described the atoms 
as ‘solid, hard, impenetrable, movable particles . . . incomparably 
harder than any porous body compounded of them, even so very hard as 
never to wear or break in pieces,’ and this conception has been found 
useful in the course of the history of atomic and molecular theories, more 
so than the alternative view, associated with the name of Boscovich, which 
regarded the atoms as mathematical points or centres of force, a highly 
abstract idea, and one having no analogy in common experience. Our 
- conception of liquids has been based in the same way on the idea of moving 
particles, themselves thought of in terms of the solid state. And yet, of 
solids themselves, whilst our knowledge of their physical and mechanical 
_ properties is very extensive, our chemical information is of the most 
meagre kind. It was an old doctrine that chemical reactions could only 
proceed in the gaseous or liquid states, so that chemical action on a solid 
i was always preceded by the tearing off of atoms from the surface under 
the influence of electrical forces. That view can no longer be maintained. 
_ Chemical reactions can occur within or at the surface of a solid, but the 
experimental difficulties are sometimes such as to make the exact 
investigation of the subject a difficult matter. 
In the modern conception of a solid, the atoms are characterised by a 
regular arrangement in space, that arrangement being repeated so as to 
