melcher: change of density of sulphur 431 



variations of topography in a sense compatible with isostasy. 

 If too the forces to which crushing is due do not vary with depth 

 and if the rocks are equally brittle, the compensation will also 

 be uniformly distributed, except perhaps very close to the surface. 



If a mountain range were to form as here suggested, infiltra- 

 tion would begin at once and the range would grow heavier 

 unless erosion at least counterbalanced infiltration. A very an- 

 cient range might be peneplained without disturbance of iso- 

 static equilibrium; if erosion were to proceed pari passu with 

 infiltration, but that being vastly improbable either a positive 

 or a negative anomaly might be induced. 



Far be it from me to assert that the formation of voids explains 

 orogeny; but it appears to be a vera causa giving results of the 

 order of magnitude demanded and to be worthy of consideration 

 in tectonic theory. 



GEOPHYSICS. — Note on the change of density of sulphur with 

 ruptured A. F. Melcher, Geological Survey. Communi- 

 cated by George F. Becker. 



A.t the suggestion of Dr. G. F. Becker a few determinations 

 have been made on the change, through rupture, of the density 

 of sulphur. Six trial specimens were prepared, brass tubes of 

 two different lengths and three different diameters being filled 

 with sulphur. After the density of the samples had been deter- 

 mined, they were bent as nearly into the form of a complete circle 

 as could conveniently be done and then the density was deter- 

 mined a second time. The second determination of density 

 compared with the initial determination gave the change in 

 density due to the rupture of the sulphur in bending. 



The preparation and filling of the tubes with sulphur were not 

 as easy as at first it would seem. Three of the tubes were 9 

 inches long with an internal diameter of 0.6 inches. The other 

 three tubes were 12 inches long and of two different diam- 

 eters, two of the tubes having an internal diameter of 0.4 inches 

 and the remaining tube an internal diameter of about 0.5 inches. 

 The tubes were first annealed to insure easy bending without 



' Published with the permission of the Director of the U. S. Geological Survey. 



