FROZEN WELL. 199 



earthen ware. Around the base several caves have been dug, from whose extremity 

 chimneys rise to the surface. In the summer, when the thermometer above is 78, there 

 issues from these caverns currents of air at 44. Many similar cases are quoted, partly 

 natural and partly artificial, from Naples, St. Maria, near Terni, at Chiavena, on Lake 

 Lugano, &c., all showing analogous phenomena. 



More recently, Sir Roderick I. Murchison, in his Geology of Russia, (vol. I, p. 186), 

 describes certain frozen caverns at Orenberg and Indersk on the Siberian side of the Ural 

 Mountains, which are quite similar to those just described. They occur in hills of salifer- 

 ous gypsum, which have openings at the top and the bottom, as in the Alps, and at Monte 

 Testaceo. In spite of the ingenious theory of Sir John Herschell, of alternate descending 

 waves of heat and cold, Sir Roderick regards the views of Prof. Pictet as the most prob- 

 able, and quite sufficient to explain the Russian caverns. In these, the freezing for the 

 most part takes place in the summer, and in winter the ice thaws ; probably because the 

 evaporation is so abundant and the air so dry in the summer, and so different in winter. 



About two miles north of Brandon village is a cavern in a hill where ice is found most 

 of the summer ; but we cannot give details. A more striking example is an old iron mine 

 at Port Henry on the west side of Lake Champlain. Ice is found here at a depth from 

 50 to 100 feet through the summer, and one of our number (c. H. H.) noticed a current 

 of cold air issuing from the opening, as in the European caverns that have been described. 

 The excavation is continued a considerable distance along the side of the valley, and one 

 or two adits exist there, through which, and the perpendicular shaft where the ice is, the 

 air current passes. This case of course is explained as the cold in the European 

 caverns. 



AVe have met with some facts respecting the frozen soil of Siberia, which seem to have 

 some bearing upon the Brandon case. According to M. Erman, the ground in northern 

 Siberia thaws during the summer from four feet eight inches, to six feet three inches. 

 A well at Yakootsk was dug or blasted in the frozen earth, to the depth of 42 feet, in fine 

 sand and clay ; and such was its temperature that Erman calculated that it would need to 

 be carried to the depth of 630 feet before reaching the bottom of the frost. (Lippmcotfs 

 Gazetteer, Art. Yakootsk.) M. Middendorf bored in Siberia to the depth of 70 feet, and 

 " after passing through much frozen soil mixed with ice, he came down upon a solid mass 

 of pure transparent ice, the thickness of which, after penetrating two or three yards, 

 he did not ascertain." The same author says that in a shaft sunk in clay, sand and lig- 

 nite, mixed with ice, the frozen crust was not passed through at the depth of 384 feet ; 

 though the temperature gradually rose from 1 at the surface to 26.6 at the bottom. 

 M. Helmersen fixes the thickness of the frozen crust between 300 and 400 feet. In a pit 

 he found a temperature of 21.2 at 75 feet deep, and 31. 1 at 378 feet. (De La Heche's Geo- 

 logical Observer, p. 293. 



Sir R. I. Murchison describes a shaft sunk 350 feet at Yakootsk which passed through 

 60 feet of alluvium, and the remaining distance through limestone and shale with some 

 coal. The temperature in the shaft was in the summer 18 .5. (NurcMson 's Russia, Vol. 

 I, p. 189.) 



At Fort Simpson, on Mackenzie's River, in North America, in the same latitude as 

 Yakootsk (62 N".), the thickness of the frozen crust was only 26 feet. (Geological 

 Observer, p. 293.) 



