222 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



crushed rock, or the heat due to it that we can estimate as 

 probably occurring within a thousand years, be adequate to 

 account for the volcanic phenomena that may take place 

 during that period. The mechanical work expended in the 

 deformation or the disintegration of a solid must all reap- 

 pear, either as heat or as external work of some sort, and 

 the experimental determination of the heat thus produced 

 was undertaken by Mr. Mallet on a large scale. Within a 

 very small limit of error, he found, both theoretically and 

 practically, that the whole of the work consumed in crushing 

 matter, like rock, reappears as heat, the amount of which can 

 be calculated by the use of Joule's mechanical equivalent. 

 The experimental verification of these theoretical calculations 

 was only possible by means of a magnificent crushing-ma- 

 chine belonging to the locomotive works at Crewe, which 

 consisted of a large balanced wrought- iron lever, so con- 

 structed that it could be used for producing compression, 

 tension, or torsion, the load itself being produced by water 

 flowing into a cylindrical iron vessel suspended to the long 

 arm of the lever. Sixteen varieties of rock, from various 

 parts of Europe and Great Britain, were experimented upon, 

 half a dozen cubes of each kind being prepared. The specific 

 heat of the cubes experimented upon, as well as their specific 

 gravities, were accurately determined. The specific heats of 

 rocks have been so rarely ascertained that special interest at- 

 taches to Mr. Mallet's results. The lowest specific heat 

 found by him is 0.180, being that of the Dartmoor red gran- 

 ite. The largest specific heat is 0.284, being that of Caen 

 stone, a variety of oolite. A second series of experiments, 

 and those of apparently considerably greater delicacy and 

 difficulty, were for the purpose of determining the total 

 amount of contraction of the solids constituting the shell of 

 the earth, upon cooling from their temperatures of fusion 

 down to their present condition. In this class of experi- 

 ments certainly none have ever been made that attained to 

 the reliability of Mallet's results. To conduct his observa- 

 tions properly, Mr. Mallet was able to make use of the fur- 

 naces of the Barrow Works, Cumberland County, and the 

 experiments were made upon a very large scale. He finds 

 that the co-efficient of cubic contraction for the slag experi- 

 mented upon, between the temperatures of 3.680 and 53, is 



