314 Intelligence and Miscellaneous Articles. 



which are very friable, have been brought from various localities 

 and yet retain their angularity, were thought sufficient evidence for 

 their transportation by ice. The majority showed no ice-scratches; 

 but the small proportion of scratched stones in the moraine matter 

 borne away on an iceberg, and the small percentage of ice-scratched 

 boulders in many deposits of glacial drift, show that the absence 

 of these striae is not inconsistent with the glacial origin of the in- 

 cluded fragments. Besides this, the stores of the Greensand con- 

 sisted of rock from which ice-marks would readily have been re- 

 moved by the action of water. The authors stated, however, that 

 they had found more positive evidence in a stone which was unmis- 

 takably ice-scratched, consisting of a siliceous limestone, and pre- 

 served in the Wbodwardian Museum. The fauna, so far as it proved 

 any thing, suggested a cold climate ; though abundant, the species 

 were dwarfed, in striking contrast to those of the Greensand of 

 Southern England and the fauna of the succeeding Chalk. The 

 authors concluded that a tongue of land separated the Upper- Green- 

 sand sea into two basins, the northern of which received icebergs from 

 the Scottish-Scandinavian chain ; the climate of this was cold, that of 

 the southern basin much warmer. 



XL. Intelligence and Miscellaneous Articles. 



ON THE ELECTRICAL RESISTANCE OF METALS. BY M. BENOIST. 



TT has long been known that the electrical resistance of metals 

 -*• increases as their temperature rises. This increase has been 

 measured up to 100 c by M. Becquerel and by Matthiessen, and to 

 200° in some metals by M. Lenz and, more recently, by M. 

 Arndtsen. I proposed to myself to trace the variation beyond 

 these limits, and to determine the increment of specific resistance 

 at very high temperatures. 



Calling cc the specific resistance of a metal (that is to say, its re- 

 sistance in unit length and unit section), the resistance of a wire of 

 the same metal of length I and section s is, according to Davy's laws, 



s 



or, substituting for 5 its value as a function of the volume Y, 

 weight P, and density D, of the wire, 



-o eel 2 ccDl 2 



If D, P, and I are known, and if E at i° be determined, the value 

 of the specific resistance at that temperature can be deduced from 

 the last relation. 



To measure E, I have chiefly employed the differential-galvano- 

 meter method of M. Becquerel. The current from two Daniell's 

 elements was divided into two equal parts, which passed, in oppo- 

 site directions, through the two wires of a very delicate differential- 

 galvanometer. The wire to be studied was intercalated in one of the 



