120 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



Depth. Temperature. 



Prussiau Feet. Eeaumur. 



700 15.654 



900 17.849 



1100 ]9.943 



1300 21.931 



1500 23.830 



There results from these measurements a very remarkable 

 but well-established result that the rate of increase of tem- 

 perature is continuously growing less as we descend. This 

 increase diminishes at the rate of one twentieth of a deo^ree 

 for every hundred feet, so that it is easy to compute at what 

 depth the temperature will cease to increase. This depth 

 is found to be the very moderate one -of 5190 feet, at which 

 a temperature of about forty degrees might be expected to 

 prevail. Even if we do not attribute absolute accuracy to 

 these observations, yet we see that a constant temperature 

 must be attained at a depth far within twenty miles ; and 

 that the temperature itself even at that depth must be far 

 less than the melting-point of the rocks. The result of these 

 observations at Sperenberg is therefore completely in accord- 

 ance with tliose deduced by Vogt from operations at the ar- 

 tesian well at Grenelle ; and if we attribute any value at all 

 to these calculations, they seem to give a death-blow to the 

 Plutonic theories of former geologists. Verhandl. JVatiirhist. 

 Vereins, Bonn^ XXXI., 267. 



EARTH TEMPERATURE AT KONIGSBERG. 



The results of a series of measurements of the temperature 

 of the earth, as made at different depths in the botanical 

 garden at Konigsberg, has been communicated by Dr. Dorn 

 to the Physical and Economical Society of that city, who re- 

 marks that while the series is of too short a duration to jus- 

 tify a very extended investigation, yet one thing is remarked, 

 viz., that the annual mean temperatures as derived from the 

 deeper thermometers are invariably lower than those derived 

 from the surface thermometers instead of beinsj hio^her, as is 

 usually the case. This anomaly, however, is abundantly ex- 

 plained if we consider that the winters of the years 1869, 1870, 

 and 1871 were of an exceptionally low temperature; and this 

 wave of cold had, in 1873, only just reached the depths in 

 the earth at which the lower thermometers were placed, 



