78 Intelligence and Miscellaneous Articles. 



from the surface. There are other mines in the same vicinity in a 

 like frozen state. 



From what we know of the depth to which frost usually pene- 

 trates into the earth, it does not appear probable that it could have 

 reached the depth of 200 feet through the solid rock in the 

 Stevens Mine, nor even through the crevice matter of the lode, 

 which, as we have stated, is as hard as the rock itself. The idea, 

 then, of the frost reaching such a depth from the outside being 

 utterly untenable, I can see no other way than to fall back upon the 

 Glacial era of the Quaternary. Evidences of the Grlacial Period 

 are found all over the Rocky Mountains. Just above the Stevens 

 Mine there are the remains of a moraine nearly a mile long, and 

 half a mile wide. The debris of this moraine consists of small 

 square and angular stones, clearly showing that they have not come 

 from any great distance. And just over the range, on the Pacific 

 slope, there are the remains of the largest moraine I have ever 

 seen, consisting of felspathic boulders of immense size. I con- 

 clude, therefore, that it was during that period of intense cold that 

 the frost penetrated so far down into these rocks, and that it has 

 been there ever since, and bids fair to remain for a long time to 

 come. — Silliman's American Journal, December 1874. 



ON THE MIXTURE OF COLOURS IN BINOCULAR VISION. 

 BY W. VON BEZOLD*. 



The Author has succeeded in clearing up and reconciling the 

 divergent observations of different observers on the mixed colours 

 produced when the two eyes receive light of different colours. 

 Some, as Dove or Ludwig, assert most positively that it is possible 

 to obtain a combined colour by the binocular fusion of two images 

 of different colours; while Franke, Helmholtz, and others advance 

 precisely the contrary. 



According to the Author, the combined tint is obtained when, 

 with one and the same accommodation, the differently coloured sur- 

 faces are both at the distance of distinct vision. When this is not 

 the case, there is a struggle between the two visual fields, and one 

 or the other prevails. — Biblioiheqae Universelle, Archives des Sciences, 

 No 202, p. 184. 



EXPERIMENTAL STUDIES ON THE ELECTRICAL RESISTANCE OF 

 METALS AND ITS VARIATION UNDER THE INFLUENCE OF TEM- 

 PERATURE. BY RENE BENOITf. 



Resuming the important question of the electric conductivity of 

 metals, M. Benoit first measured very accurately the specific resist- 

 ance of a number of them at 0° C. For this he operated compara- 

 tively with two different methods — that of the differential galvano- 

 meter, and that of the Wheatstone bridge ; and he made numerous 

 determinations on various specimens of each metal. The following 

 Table contains the means of all the results, which are referred to 

 the two units now most generally adopted for the measurement of 



* Pogg. Ann. Jubelband, p. 585. 



t A thesis presented to the Paris Faculty of Sciences. 



