424} Proceedings of the Royal Society, 



ing to different depths, agrees perfectly with what has hitherto been 

 observed under similar circumstances. As we descend, the curve 

 becomes more even, and flatter, the range rapidly diminishing, and 

 the epochs of minimum, mean, and maximum temperature occur 

 later. 



II. The mean temperature of the soil appears to increase as we 

 descend (this has been observed at Brussels and elsewhere). At 

 the Experimental Garden the mean annual temperature is, at 3 feet 

 (French), 45°.54Fahr.; at 6 feet, 46^.70; at 12 feet, 46°.90 ; at 

 24 feet, 47°.28. The Craigleith observations are ambiguous in this 

 respect. 



III. The annual ranges at the three stations and at the different 

 depths, are the following : 



3 Feet. 6 Feet. 



Observatory. Garden. Craigleith. Observatory. Garden. Craigleith. 



Fahrenheit, 18°.95 19°.65 17°.25 ir.9 14°.95 13°.9 



Centigrade, 10 .53 11 .23 9 .58 6 .61 8 .30 7 .72 



12 Feet. 24 Feet. 



Observatory. Garden. Craigleith. Observatory. Garden. Craigleith. 

 Fahrenheit, 5°.5 7°.55 9°.4 I ".45 2M 4°.l 



Centigrade, 3 .05 4 .19 5 .22 .80 1 .16 2 .28 



Now it is known by theory that the range ought to diminish in 

 geometrical progression as the depths increase arithmetically ; and 

 accordingly these results may be very closely represented by loga- 

 rithmic curves, having different Moduli at each station, depending 

 on the nature of the soil. If A denote the range in Centigrade 

 degrees at a depth jo, and A and B two constants, we have 

 Log. A^ = A + Bp 



/specific heat 

 And B depends upon ^/ conductivity o^ the soil. Now this con- 



stant B is found to have the following negative values ; * 



Observatory —0.0547 ; Garden — 0.0440 ; Craigleith — 0.0317. 



Consequently the conducting power of the strata is in the order 

 just written, the first being the lowest, the last the greatest (sup- 



* In order to render the results directly comparable with those in M. 

 Quetelet's excellent paper in the Brussels Transactions, the French foot 

 and Centigi-ade degree are employed as unities. 



