REVIEWS. 



405 



On comparing the results obtained in Dolcoath in 1821-22 and 1827, it appears 

 that the temperature was increased only 4^* in one level, with an increased depth 

 of 252 feet, giving a ratio between the stations of 1° increase in 63 feet ; and in 

 another level the tfmjie! iinive was actually 2° to 2" 5' less than in 1822, although 

 252 feet deeper than the mine was then. " These experiments." Mr. Fox says, 

 *• were made with grea,t care, and this exceptional case may probably be due to 

 the sreater hardness and compactness of the lode in the deeper level and the 

 diminished quantity of water," 



The depth of Tresavean was increased 540 feet betAveen 1837 and 1853, and 

 the temperature 8*^ 5' in the deepest level, or in the ratio of 1*^ in 63 5 feet. 



Mr. Fox has not included in the above tables the recent results in the United 

 Mines nor Fowey Consols, the experiments'not having been made in the dpepest 

 levels; but the hot spring at 116°, at the depth of 255 fathoms in the United 

 Mines, gives a ratio of 1" increase in in 23-2 feet ; and the rock in another level, 

 also 255 fathoms deep, 1° in 47 feet. 



In 1853. the bottom of the United Mines was 275 fathoms, and the rock 94", 

 or in the ratio of 1° in 37"5. At Fowey Consols, the rock, in a level 288 fathoms 

 deep, was 93°, or in the ratio of 1° in 40'2 feet. 



"Widely," continues Mr. Fox, " as the ratios differ from each other in different 

 mines and in different parts of the same mine, the results tend to confirm the 

 statement that the temperature in general increases less rapidly in deep mines 

 than in those which are of inferior depth ; and this is more especiallj'- observable 

 when experiments are made, from time to time, at the bottom of a mine as the depth 

 increases, iinless the results be modified by an increase of water coming from 

 greater depths. It is not, however, to be inferred that the diminishing ratio of 

 temperature in descending into the earth extends to an indefinite depth ; it may, 

 on the contrary, and probably does, increase much more uniformly at depths 

 where the circulating water has little or no influence." 



" A copious spring of warm water gushing from a vein is hailed by the miners 

 as a favourable indication of the proximity of ore, and so is a pervious or 

 * hollow ' lode ; but the former clearly results from the latter, the warm water 

 rising through the lode." 



Mv. Fox then briefly remarks upon the qualities of these subterranean waters, 

 and the general absence in them of saline or mineral matter at their issue ; 

 while, on the other hand, it is observed that the water collected in the pools in 

 the levels frequently contain metallic salts derived from the ore-heaps broken 

 from the lodes, and exposed to the joint action of air and water. The phenomena 

 observed in mineral veins, however, afford strong presumptive evidence that the 

 water circulating through them has, from time to time, varied much in its 

 propei'ties, sometimes depositing minerals, and at others decomposing them. In 

 concluding, Mr. Fox adds that, on comparing the specific gravities of pieces of 

 difl:erent rocks taken fi'om the deepest parts of some of the mines with others of 

 the same kind occurring at or near the surface, he has not found any decided 

 difference between them in that respect. 



Mr. Fox's paper is marked by a conciseness and precision which render it 

 difficult to abbreviate it, and in this abstract we have used his own expressions, and 

 have given the details as much length as possible, as there is not even a really 

 superfluous word in the original memoir. 



The Report on the Marine Zoology of Strangford Lough, in the Irish Channel, 

 by Dr. Dickie, is valuable to the geologist as well as the naturalist, as a record of 

 the characters of sea-bottom with which certain forms of mollusca are associated, 

 and for the notings of the species to which the broken and dead shells in each 

 locality dredged belonged. 



Mr Bowerbank contributes a further report on the vitality of the Spong'ad^. 

 In the former paper by this gentlemen, read at the previous meeting, his observa- 

 tions on the inhalations and exhalation of water through the pores and oscula of the 

 British marine sponge Ilyme/iiacidon caruncula were recorded, showingthe capability 

 which that sponge possesses of opening and shutting those tubula cavities at 

 pleasure. The present investigations were undertaken to determine the nature 

 and power of the imbibing pores, which can only be seen in young and transparent 



