Proceedings of the Royal Society, 425 



posing the difference of specific heat immaterial). By extending 

 the Logarithmic curve, the depth at which the range has any 

 amount maybe found.* Thus the range will be reduced to yjj^ of 

 a Centigrade degree, or may be reckoned insensible, at the follow- 

 ing depths : — 

 Observatory, 58 feet ; Experimental Garden, 72 feet ; Craigleith, 97 feet. 



Now it is remarkable that the above variations in the value of B 

 exceed those contained in M. Quetelet's table, which includes all 

 the observations made in different parts of Europe ; shewing that 

 the increase of the value of B with the Latitude, which was thought 

 to have been observed (Quetelet, Mhnoire sur les Variations Diurnes 

 et Annuelles de la Temperature Terrestre^ p. 61), was quite acciden- 

 tal ; and that the value of B must depend solely on the constitution 

 of the soil in which the experiments are conducted. 



IV. The epochs of the winter minimum of 1837 are ill deter- 

 mined for the upper thermometers, owing to the great irregularity 

 of the winter curve, and also because the observations were com- 

 menced too late to obtain them correctly. The epochs of maxi- 

 mum temperature give, however, a complete confirmation of theory 

 and of the preceding deductions. We find that, with a single ex- 

 ception (the shortest thermometer at Craigleith), and that excep- 

 tion is doubtful, all the thermometers at Craigleith attained their 

 maximum first, then those at the Experimental Garden, and lastly, 

 at the Observatory, as the following table shews : — 



Maximum at 



3 Feet. 6 Feet. 12 Feet. 24 Feet. 



Observatory, August 6. September 2. October 1 7. January 8. 



Exper. Gar. July 31. August 24. October 7- December 30. 



Craigleith, August 5. August 19. September 11. November 11. 



We also find, as theory assigns, the retardation of the maximum 

 increases arithmetically with the depth. So that, if we project 

 these observations and cause an interpolating straight line to pass 

 through the points for each station, we find that the progress of heat 

 downwards is. 



At the Observatory, 1 foot in 7-5 days. 



Experimental Garden, 7-1 ... 



Craigleith Quarry, 4.9 ... 



giving the same order of conducting power as before. 



The bearing of these experiments on geological theories, and es- 

 pecially on the movement of the Isothermal lines in the interior of 

 the globe, is evident. 



December 17. — Dr Abercrombie in the Chair. The follow- 

 ing Communications were read : 



1. On the Law which connects the Elastic Force of Vajx)ur 

 with its Temperature. By John Scott Russell, Esq. 



* The values of A are 1.164, 1.176, 1.076 in the same order as before. 

 VOL. XXVI. NO. LII. APRIL 1839. E 6 



