The Value of Earth Temperatures. 13 



There are great difficulties attending such experiments, viz : — 



1st. — There is the difficulty of obtaining Thermometers of 

 sufficient lenghts. 



2nd.^ — There is the difficulty of obtaining a site corresponding 

 to the mean sea level, which clearly ought to be the starting point 

 from which such observations should be made. 



3rd. — There is the difficulty of providing for a regular systematic 

 set of observations, which, as a general rule, can only be carried 

 out at a public Observatory, to answer the previous conditions. 



The first enquiry from such experiments would naturally be 

 the important question as to the existence of a great internal fire. 

 This theory would be borne out, not only by the laws of mechanics, 

 but by the observations which have so repeatedly been made in 

 Artesian wells and in Coal Mines. 



The general results arrived at from experiments, appear to 

 prove that the temperature of the earth increases at the rate of 

 1° Fahrenheit for every depth of 55 or 60 feet. 



It is remarkable that Humboldt, whilst he admits this fact in 

 a variety of instances, yet seems inclined in his " Cosmos" to 

 doubt whether the temperature of the earth does increase or 

 decrease as we descend beneath the surface. But we must re- 

 member that when Humboldt wrote his " Cosmos" no systematic 

 observations of Earth Temperature had been carried on. And 

 even at the present time I have the greatest difficulty in obtain- 

 ing such observations. 



So far as I am aware, the only observations of this class have 

 been made at Greenwich, Edinburgh, Kew, Paris, and Melbourne, 



Paris would, perhaps, afford the most satisfactory results, for 

 one reason especially, as being on a comparatively low level. But 

 I am sorry to say that I have no records of any observations of 

 earth temperature made there. The same with Kew — the same 

 with Melbourne. Yet, no doubt, very valuable results might be 

 obtained from all these places. 



No doubt there is very great difficulty in carrying on these ex- 

 periments, and I would hardly have ventured to bring this question 

 forward to-night, if I had not been requested to do so. 



The Thermometers exhibited in the hall this evening are of the 

 following lengths, viz : — 



JS T o. 1 



„ 2 



,, 3 



„ 4. ... 



„ 5. ... 



These Thermometers were supplied by Mr. Grimaldi, of Mel- 

 bourne, and I am bound to say that he has discharged his duty 

 in the most efficient manner. 



20 feet 



11 



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6 



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3 



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