170 MR. J. C. DYER ON THE ORIGIN OF 



tific value, because the compressiiig forces employed by 

 Canton and by him were so widely different. Mr. Canton 

 had applied the pressures from half an atmosphere, or from 

 7g lbs. to 30 lbs. per square inch, while Perkins used pres- 

 sures from 50 to 400 atmospheres, from 750 lbs. to 6000 lbs. 

 per inch. The same rate of compression appeared in all 

 his experiments ; and as this was the same as that shown 

 by Canton, they may together be taken as proving the law 

 of equal compression by equal forces. It will most likely 

 be established that the same law will apply to all solid bodies 

 as well as to liquids and vapours, unless the solids be dis- 

 rupted by the forces. In short, that all known bodies are 

 elastic will ere long become an admitted property of pon- 

 derable matter may be safely predicted; thus disposing 

 of the supposed division of material ponderable bodies into 

 elastic and non-elastic. 



The apparatus employed by Mr. Perkins was, first, a cast- 

 iron cylinder, the sides and bottom 3 inches thick, with a 

 moveable top of equal strength. This, filled with water, 

 had a force-pump, as in the hydraulic press, to measure the 

 forces applied by the leverage and size of the induction 

 pipe. 



Second, a small brass cylinder, with a piston fitted to 

 slide in it, water-tight -, the cylinder half an inch in dia- 

 meter, and of the length to have a column of ten inches 

 long under the piston when drawn up to the end. The 

 piston-rod was graduated into divisions of 100 to the inch, 

 and a sliding-ring fitted on it, so as to be pressed up on 

 the rod as this was forced down upon the enclosed water, 

 thus marking the descent in y^^ parts of an inch. The 

 brass cylinder being under the same water-pressure inside 

 and outside, was not subject to any strain to alter its 

 capacity. 



Third, when the external pressure was removed, the 

 water in the brass cylinder would of course expand to its 



