Observations of Underground Temperature. 



33 



Table II. — Rates of Logarithmic Diminution in Amplitude, 

 and of Retardation in Epoch, of Annual Harmonic Variations' 

 Downwards. 



II 



Calton Hill. 



Experimental Garden. 



Craigleitli Quarry, 



WW 



'■3 |<2 ° 



"S'E,° o 

 "a o,o 

 jj.fcJt 



E ij O 



•3*3 o 

 1.2 U 



O § 3 -a 



« o a 



■§ Si 3 g 

 ■S B o.J 

 •5.2.2 ° 



Hi! 



Ph o'C p. 



° o 3^ 



Bate of diminution 

 of Napierian loga- 

 rithm of amplitude 

 per foot of descent. 



111 . 



1.2 || 



feet. 

 3 to 6 

 6 to 12 

 12 to 24 



•1259 

 •1206 

 •1101 



•1176 

 •1176 

 •1129 



•1004 

 •1130 

 •1084 



•1163 

 •1193 

 •1062 



•09372 

 •06304 

 •06176 



•06599 

 •06690 

 •06690 



3 to 24 



•1151 



•1149 



•1082 



•1114 



•06841 



•06648 



16. All the numbers here shown for each station would be 

 equal, if the conditions of uniformity supposed in the theoretical 

 solution were fulfilled. The discrepancies are, with the excep- 

 tion of one of the numbers for Craigleith Quarry, on the whole 

 small ; smaller, indeed, than might be expected when the very 

 notable deviations of the true circumstances from the theoretical 

 conditions are considered. The mean results over the 21 feet, 

 shown in the last line, present very remarkable agreements, — the 

 numbers derived from amplitudes being identical with that 

 derived from epochs for the Calton Hill station, while the dif- 

 ferences between the corresponding numbers for the two other 

 stations are in each case only about three per cent. Taking 

 that one number for the first station, and the mean of the 

 slightly differing numbers derived from amplitudes and from 

 epochs respectively for the second and third, we have undoubt- 

 edly very accurate determinations of the value of kJ -j- for the 

 three stations, which are as follows : — 



Calton Hill trap rock. 



Experimental Garden 

 sand. 



Craigleith Quarry 

 sandstone. 



«/?-»" 



v/.™ = -1098 



v k 



x/l£= -06744 

 v k 



A continuation of the observations at Calton Hill not only 

 leads, as we shall see, to almost identical results, both by dimi- 

 nution of amplitude and by retardation, on the whole 21 feet, 



Phil Mag. S. 4. Vol. 22. No. 144. July 1861. D 



