182 



MR THOMAS HEATH ON 



SEMI-ANNUAL TERM. 







Feet. 



Semi- 

 Amplitude. 



Dates of 





Maxima. 



Minima. 



Old *, . 



New t x . 

 Old t 2 . 

 New t~ 2 . 

 Old t 3 . 

 New t 3 . 

 Old t 4 . 

 New t i . 





25-6 



21-0 



12-8 



11-1 



6-4 



5-0 



3-2 



31 



0-020 

 0-041 

 0-120 

 0-133 

 0-400 

 0-458 

 0-705 

 0-719 



May 11-9, November 10 '5 

 April 28-6, October 28"2 

 March 16-7, September 15"3 

 March 6-3, September 4"9 

 February 18-9, August 20"5 

 February 5 - 8, August 7 "4 

 February 5 - 7, August 7 '3 

 February - 8, August 2*5 



February 9-6, August 11 3 

 January 27 -3, July 28'9 

 December 15'6, June 16'0 

 December 5 - 2, June 5 - 6 

 November 19-9, May 21 '2 

 November 6 "7, May 8'1 

 November 6-6, May 8-0 

 November T7, May 3'2 



We are now in a position to deduce the conducting power of the rock, both from 

 the Napierian logarithms of the amplitudes, and from the retardation of phase, expressed 



/7TC 



in circular measure. We have the two values of /^= Alog e a= Ar, where T is 



the period, one year for the annual term, and half a year for the semi-annual. 



The following table gives the values of r x and r 2 in circular measure, and the 

 Napierian logarithms of a x and a 2 . 





Depth. 



r i 



V 2 



Log, fflj 



Log, a 2 





Feet. 











Old t x 



25-6 



1-553 



3-457 



-0-467 



-3912 



h 









12-8 



2-920 



5-391 



+ 0-835 



-2-120 



h 









C-4 



3-654 



6-278 



+ 1-568 



-0-916 



h 









3-2 



4018 



6-735 



+ 1-962 



-0-350 



New tj 









21-0 



2-013 



3910 



-0-066 



-3-194 



h 









111 



3-136 



5-744 



+ 0-993 



-2-017 



h 









5-0 



3-847 



6-723 



+ 1-709 



-0-781 



h 









31 



4-068 



6-894 



+ 1-943 



-0-329 



If we now take every possible combination of two thermometers from the four in 

 each set, and divide the differences of their retardations of phase, and of the logarithms of 

 their amplitudes, by the difference of depth in feet, we get the following two tables 



7TC 



showing the values of K f -j- for the annual and the semi-annual terms. 



