170 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



gested, in explanation of this, that there was a temporary de- 

 pression of this western salt-area, permitting the deposition 

 of the lower fossiliferons limestones from the outer ocean, 

 upon the saliferous series; after which a second movement 

 of the surface excluded the ocean for a considerable period 

 while the upper dolomites were laid down, to be in their turn 

 covered by the Corniferous limestone. A shaft now being 

 carried down for the purpose of working these beds of rock- 

 salt will permit the paleontological study of the question. 



SUBTERRANEAN TEMPERATURE. 



The observations on the temperature made in the deep 

 boring at Sperenberg, near Berlin, in Prussia, have of late 

 attracted considerable attention. The depth penetrated here 

 is 4052 Rhenish feet (4172 feet English), the whole distance 

 being in rock-salt, with the exception of the first 283 feet, 

 which were in gypsum and anhydrite. The early observations 

 were unsatisfactory, and, as since appears, incorrect. They 

 showed a greatly diminished rate of increase in descending, 

 from which Mohr reasoned to the absence of any subterra- 

 nean heat. His conclusions are, however, rejected as falla- 

 cious by Dunker, to whom we owe the observations on the 

 temperatures in this boring. The first determinations of the 

 latter were found to be vitiated by the circulation of water 

 in the bores, which, it was shown, was the cause of a consid- 

 erable reduction of temperature. This source of error was 

 subsequently obviated by the use of plugs at suitable dis- 

 tances; and, from the corrected observations thus obtained, 

 it was found that although there were still considerable va- 

 riations in the rate of increase, as determined for intervals of 

 200 feet down to 3390, the mean rate of increase in the tem- 

 perature was one degree of Fahrenheit for 50 Rhenish or 51.4 

 English feet a figure agreeing closely with those previously 

 deduced from many observations in other localities. The 

 rate of increase for the upper 700 feet, which were partly in 

 gypsum and anhydrite, was found to be 3.24 degrees for 

 each 100 feet, while for the distance from 2100 to 3390 feet 

 it was only 1.49 degrees. From some recent experiments 

 undertaken in connection with this problem, llerschel has 

 found that the conductivity of rock-salt is exceedingly high, 

 and, according to him, "theory shows that the rates of in- 



