DIFFERENTIAL PRESSURE ON MINERALS AND ROCKS 491 



the material to be experimented upon, and then filHng the space 

 between the two with some embedding material which may be 

 poured in as a liquid but which on cooling will solidify into a mass 

 which is susceptible of deformation under pressure and which can, 

 at the conclusion of the experiment, be removed by heat or in solu- 

 tion. The whole is then submitted to the action of a powerful press 

 and squeezed down. The resistance to deformation offered by the 

 copper as well as by the embedding material itself is transmitted 

 through the embedding material to the specimen, which thus receives 

 a very considerable amount of lateral support, or is submitted to a 

 very considerable amount of lateral pressure as the deformation 

 proceeds. After the completion of the experiment the embedding 

 material is removed and the specimen recovered and examined. 

 This method is easily followed, experiments can be made quickly, 

 and but little mechanical skill is needed in preparing the materials 

 for the purposes of the experiment. It can, however, be used only in 

 experiments carried out at ordinary temperatures, and it is impossible 

 in using it to determine accurately the pressure to which the specimen 

 is being subjected, for the pressure is divided between the box, the 

 embedding material, and the specimen itself. Furthermore, the 

 pressures which are obtained by this means are not so great as it is 

 desirable to employ in some cases. Kick, however, succeeded in 

 this way in developing permanent deformation in rock salt, talc, 

 gypsum, fluorspar, and marble. Two papers by Rinne,^ which 

 have appeared more recently and while the present investigation 

 was being carried out, also present an account of certain experiments 

 in which Kick's method was employed and in which rock salt, 

 sylvine, and marble were deformed. 



In the present investigation stout copper pipe was used, the 

 standard size known as "one-inch iron-pipe size" being usually em- 

 ployed. This has an internal diameter of i . 063 inches and is made 

 of material having a thickness of i . 125 inches. From this lengths were 

 cut off to suit the specimen to be examined. The piece of tube, having 

 smoothly finished ends, was placed in an upright position on a glass 



I "Beitrag zur Kenntniss der Umformung von Kalkspatlikrystallen und von 

 Marmor unter allseitigem Druck," Neues Jahrh. jiir Min., etc. (1903), I, 3, s. 160; 

 "Plastische Umformung von Steinsalz und Sylvin unter allseitigem Druck," ibid. 

 (1904), I, 3> s. 115- 



