
PROFESSOR FORBES ON THE TEMPERATURE OF THE EARTH. 209 
Also p,, Por, Pou Aenoting the depths corresponding to a range of 1°, 0°1, 0°01 
Cent., we have 
1+A 
2+A 
Pui = — B 
Po-01 — whle . 

yn=- 
bol 
Numerical Example. By the projection for 1837, Plate IX., we find 
Observatory. Experimental Garden. Craigleith. 
The superficial range 14°-6 Cent. 15°-0 Cent. 11°-9 Cent. 
Pi=depth where range=10° Cent. 3:0 F. ft. 4:0 F. ft. 2-4 ¥F. ft. 
Whence A : : : : 1:164 1:176 1:076 
B ; : : ‘ .  —0°0547 — 0:0440 —0:0317 
Bin i : : ‘ ‘ , ; 21:4 F. ft. 26-7 F. ft. 341 F. ft. 
Por 39°7 49°5 65-7 
Poot 58:1 12:2 97:3 
The numbers in the last line may be taken (arbitrarily) as a limit of compa- 
rison for the point at which the annual variation sensibly vanishes, and its dif- 
ference in the three stations shews the marked influence of the conducting soil 
or rock. The following tables contain a summary of these results for five years. 
TABLE X. SHEWING THE VALUES OF A AND B.* 

VALUES OF A. 
VALUES OF B. 















Experi- _ | Experi- 
Ob eee | erent Craigleith. phos mental | Craigleith. 
LOD. Garden. J: Garden. 
1837 1:164 1:176 1:076 1837 |—-0545 | —-0440 | —-0316 
1838 1173 1°217 1114 1838 |— :0641 |—-0517 | —-0345 
1839 1:086 1:182 1:049 1839 |—-0516 | —-0498 | —-0305 
1840 1:073 1155 1:044 1840 |—-0550 | —:0470 | —-0308 
1841 1:031 1141 1:019 1841 |—-0474 | —-0460 | —-0281 
Means, | 1°105 1174 1-060 Means, | —-°0545 | —-0477 | —:0311 
TaBLE XI. SHEWING THE DEPTHS AT WHICH THE ANNUAL RANGE IS REDUCED T0 



0°01 CENT. 
Observatory. eee Craigleith. 
1837 58'1 72°2 97°3 
1838 49°3 61:8 91:0 
1839 59-2 63°5 100-0 
1840 050°9 67°1 98°8 
1841 63:9 68:3 107:4 
Means, 57°3 66:6 98-9 




* The French foot and centigrade degree are here taken as units. 
VOL. XVI. PART II. 
oa 
