37 2 Dr. Ure’s new experimental researches 
“ tion, or greatest density, a quantity always as the square 
“ of the temperature from that point/’ He regards the law 
as resulting from the constitution of liquids, and therefore 
not applicable to solid bodies. This is indeed implied in its 
enunciation. In p. 43 , after assigning reasons, he states, 
“ that for all practical purposes we may adopt the notion of 
“ the equable expansion of solids/’ 
Now I am prepared to prove, either, that the expansion of 
solids partakes of the above inequability of liquids, which 
nobody imagines, and for which no reason, even hypothetical, 
can be assigned ; or, which is the only alternative, that homo- 
geneous solids, and mercury, proceed almost exactly, pari 
passu , in their rates of expansion by heat. 
The experiments which justify this assertion were made 
by me about five years ago, and were then exhibited to many 
of my chemical friends, as also in my public lectures ; but a 
wish to render the series more complete, has induced me to 
withhold them from the public eye, till requisite leisure could 
be afforded for this purpose. They were performed with a 
pyrometer of peculiar construction, in an oblong trough filled 
with melting ice : a strong bar of Swedish iron was placed, 
from which projected at right angles, four inflexible iron 
arms, attachable by powerful screws to any part of the bar. 
The arms nearest the extremities of the bar, carried each a 
fine micrometer microscope, made by that admirable artist 
Mr. Troughton. The other two arms were incurvated down- 
wards at their extremities, which supported a metallic or 
other rod. This was fixed by two pinching screws at one end, 
but lay loose on a friction roller at the other. The loose end 
bore an elevated index. The curvature of these two arms was 
