14 Mr Fisher, On the effect of Convective Ctirre7its [Nov. 20, 



November 20, 1876. 

 Prof. J. Clerk Maxwell, F.R.S., President, in the chair. 



The following Communications were made to the Society by 



(1) Mr O. Fisher, M.A., On the Effect of Convective Currents 

 upon the Distribution of Heat in a Borehole. 



This paper was supplementary to one read by the Author on 

 Nov. 29, 1875. The temperatures observed in the boring at 

 Speremberg near Berlin, which attained a depth of upwards of 

 4000 feet, were reduced to a mean law by Professor Mohr of 

 Bonn\ and shewn by the Author to conform closely to those 

 expressed by a parabolic curve, having its axis horizontal, and 

 its vertex as a depth of 5171 feet, expressed by the equation 



F = - ^ ^^ + 0-012982^ + 71817, 



F being the temperature expressed in E.eaumur's scale, and x the 

 depth. 



Previous observations on underground temperature having led 

 to the conclusion that the temperature curve within the earth's 

 superficial strata is a straight line, expressing an increase of 

 temperature varying as the increase of depth at the rate of 

 1** Fah. for about 50 to 60 feet of descent, the object of the 

 present paper was to shew that the deviation of the curve from 

 the rectilinear towards the parabolic form at Speremberg was due 

 to convection currents. 



An elaborate account of the Observations taken in the Sperem- 

 berg boring has been given by Dunker in a paper entitled "Ueber 

 die Benutzung tiefer Bohrlocher zur Ermittelung der Temperatur 

 des Erdkorpers und die desshalb in dem Bohrloche I zu Speren- 

 berg auf Steinsalz angestellten Beobachtungen." Von Herrn 

 Dunker in Halle a. S. 



Dunker's table shews that, when these currents were inter- 

 rupted, the temperature of the water in the borehole fell in the 

 upper part of the boring for a depth of somewhere between 100 

 and 300 feet, and below that depth rose, the difference between 

 the temperatures taken when the currents were interrupted and 

 when they were not so amounting sometimes to nearly 2° R. It 



1 See Nature, Oct. 21, 1875. 



