ANNIVERSARY ADDRESS. 29 
modify our views as to elements by ‘correcting terms”? Long 
ago, Faraday drew attention to the supposed absolute similarity 
of molecules in the phrase that they behave like ‘“‘ manufactured 
articles.” This phrase has been worn rather bare in the course 
of its use in theological argument, and was long ago shown by 
Clifford to be a statement going beyond what is known of the 
facts. In the case of sulphur, so far from the molecules being 
almost identical, they have no more than a family likeness, and 
form groups with properties gradually changing from the most 
stable amorphous variety on the one hand, to the quite stable 
crystalline variety on the other. I am persuaded that the high 
and dry view of the absolute similarity of molecules as roughly 
taught in text books has done much harm as well as good, and 
the science of chemistry is now sufficiently advanced to allow 
the more correct view to be habitually used without disadvantage. 
One consequence of the chemical theory of electricity—we will 
not quarrel as to the name, though, as a matter of fact, there 
must be a new science lying equally behind both electricity and 
chemistry—is that the possibility of charge without the interven- 
tion of free atoms cannot be admitted. It was for this reason that 
in 1889 I suggested a purely chemical theory of the action of the 
ordinary frictional machine, in which I postulated the decom- 
position of glass or water or both as a consequence of mechanical 
friction. The idea was new to me at the time, but it has probably 
been advanced before. At that time I had made a few experi- 
ments on the change of composition produced by pressure on 
complex substances, with the result that the majority of the 
substances I examined had their melting points changed when 
pressed with as high a pressure intensity as soft steel will bear. 
Since then I have made a good many more experiments which 
I have not published hitherto, as they were perhaps too informal 
and intermittent, but the general result has been with some 
exceptions the same. Since then Mr. Carey Lea, in America, 
succeeded in decomposing substances by rubbing them in # 
mortar, and that in at least one case where rise of temperature 
