Intelligence and Miscellaneous Articles. 245 



ELEVATION OF LAND DURING THE GLACIAL PERIOD. 



[We have been requested by Prof. Dana to insert the following 

 Note in order to correct any wrong impression that might possibly 

 be formed by the reader from the statement of Dr. Croll on page 93 

 of our last Number. — Ens.] 



The opinion advocated formerly, and now, by Mr. Dana is that 

 the more northern lands (or, in later papers, portions of northern 

 lands) w T ere more elevated than now during the era of increasing 

 and maximum ice, or the era distinguished by him as the Glacial 

 period ; that this era was followed, both in America and Europe, by 

 a subsidence of the same land initiating the Champlain period, and 

 that this was the era of melting, and of the spreading of mammals 

 northward, an impossible occurrence in America during the Glacial 

 era ; that another era of ice of much less extent occurred subse- 

 quently in Europe, if not also in North America, probably com- 

 mencing with the epoch of the change in the land to its present 

 level, and that this was the occasion of the destruction of the mam- 

 mals of North Siberia, and other faunal changes. The evidences 

 believed to favour these conclusions are stated in his various papers 

 and his c Manual of Geology/ and need not be here repeated. The 

 latest discussion by him of the facts from Eastern North America 

 as to the Champlain subsidence is contained in the ' American 

 Journal of Science ' for 1882. 



Mr. Dana's opinion as to the fact of an elevation of northern 

 lands in the Glacial era (that is, the era as he defines it) was a con- 

 clusion from facts that had been observed in Europe and America, 

 and not a supposition suggested by, or thought to be sustained by, 

 any theory as to the cause of the elevation. The era of maximum 

 ice he has always supposed to be that of maximum or nearly 

 maximum cold ; and the Champlain era, following, an interglacial 

 era (for Europe at least) of milder climate, in which the Mammoth 

 and the associated mammals and other species of life, animal and 

 vegetable, of the colder temperate and temperate latitudes, reached 

 their furthest northern limit. 



ON THE CAUSES OF THE PRODUCTION OF ATMOSPHERIC ELEC- 

 TRICITY IN GENERAL, IN STORMS, AND IN HEAT LIGHTNING. 

 BY M. DE TROMELIN. 



In seeking in nature for causes capable of producing electricity, 

 I have been led to assume in the first case the friction of moist or 

 dry air against the surface of the earth or of the seas. 



Every one knows Armstrong's hydro -electrical machine. When 

 the steam emerges from the boiler, the latter is charged negatively 



