ON UNDERGKOUND TEMPERATUKE. 187 



" Assuming 49° as the surface-temperature, and adopting 70° as the tem- 

 perature at 1100 feet, we find, for the mean rate of increase downwards, 

 •0191° per foot, or 1° for 52-4 feet. 



" Comparing the first observation in the water (56°) with the temperature 

 at the bottom (70°), the mean rate of increase comes out -0165, or 1° for 

 60-6 feet. 



" During the remainder of the present year the repetition of the observa- 

 tions will be continued, and it is hoped the influence of seasonal changes will 

 be measured and eliminated. In conclusion, we have to acknowledge the 

 liberality of the New Eiver Company in allowing Mr. Symons unreserved 

 access to their grounds, and permission to erect the necessary apparatus, 

 which has been efficiently protected by their servants. " 



I desire to say, in reference to the foregoing Report, that the length of 

 time which Mr. Symons found it necessary to interpose between his observa- 

 tions is a peculiar circumstance of which I can at present off'er no sufficient 

 explanation, and I cannot help thinking that it might be obviated by some 

 modification of the arrangements. Mr. M'Farlane, in three different bores, 

 has found 15 minutes amply sufficient to give the correct temperature. Can 

 the difference be owing to the greater size and smoothness of the bore in this 

 instance off'ering less resistance to vertical currents ? 



As regards the first 210 feet, being the portion occupied by air, it is not 

 siu'prising that the influence of season should here be perceptible, seeing 

 that the well is 8 feet in diameter. The temperature of the air in an open- 

 ing of this size, even for tJie average of the year, cannot be taken to represent 

 that of the solid earth at the same dej)th, but will doubtless be found to be 

 intermediate between the latter and the mean temperature of the exter- 

 nal air. 



The Rev. Dr. Graham (Member of the Committee) has taken observa- 

 tions in a bore at Logie Works, near Dundee, tkrough the kindness of the 

 proprietors, Messrs. Edwards, from whom he received much assistance. The 

 bore was available to the depth of 640 feet, and was described, before the 

 observations, as being filled nearly to the surface with water, in which there 

 was no perceptible motion. Much difficulty was experienced from the shak- 

 ing down of the detached column of mercury in the thermometer ; but this 

 was at length obviated by fixing the thermometer horizontally in a hollow 

 cup in a piece of hard wood, which had a hinged glass cover to permit of 

 reading the indications, provision being made for the free circulation of the 

 water, and a weight being attached to the bottom to act as sinker. The 

 temperatures observed were exceedingly anomalous, being about 10° greater 

 at 100 feet than at 50 feet, then increasing to the depth of about 400 feet, and 

 afterwards decreasing to the bottom. Dr. Graham states that he and his 

 assistant observers were convinced that the water which filled the bore was 

 obtained at the depth of about 170 feet, and that while one portion rose to 

 the surface, another and smaller fiowed downwards and escaped through the 

 lower strata. 



Mr. John Hunter, Assistant to the Professor of Chemistry, Queen's Col- 

 lege, Belfast, has taken a few observations in two shafts, sunk with a view 

 to salt-mining, at high ground near Carrickfergus. In both of them the 

 water stood only to the depth of a few feet. It was found that the tempera- 

 ture of the air within the shafts increased downwards, at any one time, -with 

 tolerable uniformity, but varied greatly with the weather. The shafts were 

 kept constantly closed by boarded covers, except during the actual process 

 of observing. The temi^erature of the water at the bottom, which is as- 



