424 



Progress in Science. 



[July- 



applied to urinary deposits and other pathological specimens. The former, 

 placed in small bottles, arrived in perfectly good condition after a journey of a 

 week in hot weather. Fragments of tumours and other diseased tissues were 

 soaked in a saturated solution for forty-eight hours, until thoroughly imbued 

 with the fluid. They were then pressed, to remove superfluous moisture, and 

 tied up in thin sheet india-rubber or oil silk, and so transmitted by post. 



HEAT. 



An experiment lately made by Mr. Spence, of Manchester, seems to prove 

 that under certain conditions the diamond is combustible at a much lower 

 temperature than has been hitherto supposed. A South African diamond of 

 the size of a small pea, coated with refractory clay, was placed in a crucible 

 with a mixture of soda and hydrate of lime, and then heated in a muffle for 

 three days and three nights. On opening the mass, it was found that the 

 diamond had entirely disappeared, although the heat had never exceeded a 

 cherry-red. 



At a recent meeting of the Helvetic Academy of Sciences M. Dufour gave 

 the principal results of an experimental inquiry into the variations of temper- 

 ature which occur in diffusion of gases separated by a porous partition. He 

 had studied, among other cases, those of hydrogen and air, of air and car- 

 bonic acid ; and he distinguishes in these researches between diffusion at 

 constant pressure and diffusion with varying pressure. A porous vessel con- 

 taining the gas with slower diffusion (air or carbonic acid), and having a very 

 sensitive thermometer applied to its inner surface, was placed in a larger and 

 cloth-covered vessel, in which the other gas (hydrogen or air) was made to 

 circulate. A glass tube through the stopper of the porous vessel communi- 

 cated in some cases with the open air (constant pressure), and in others with 

 a manometer. The thermometer was observed with a cathetometer. It ap- 

 pears that with constant pressure there is always elevation of temperature on 

 the side of the entering diffusion, and lowering of temperature on the 

 side where the diffusing gas issues from the partition. M. Dufour believes 

 that this change of temperature is not produced throughout the whole gaseous 

 mass, but only at the surface of the porous partition. He points out that at 

 the side of entrance there is condensation, compression, and hence develop- 

 ment of heat ; while at the other, on the contrary, there is expansion of the 

 gas, and so absorption of heat. With varying pressure the phenomenon is 

 more complicated. The indications of the thermometer are shown by the 

 annexed curve, in which the abscissas are the times and the ordinates the 

 temperatures. 



y 



GEOLOGY. 

 Stratigraphical Geology. — Dr. Dawson has alluded in a recent number of 

 the "Canadian Naturalist" to the discussion which has reopened on the 

 terms Cambrian and Silurian, and which originated in a difference of opinion 

 between Sir Roderick Murchison and Professor Sedgwick. He agrees 

 with Dr. Sterry Hunt that the Silurian system consists of two groups, 

 which should have distinct names, and that the term Silurian should 



