Effects of Heat modified Inj Compression. 199 



greater depth of sea would, of course, be requisite to con- 

 strain the carbonic acid effectually.; and future experiments 

 may determine what depth is required to co-operate with 

 any given temperature. It is enough for our present pur- 

 pose to have shown that the result is possible in any case, 

 and to have circumscribed the necessary force of these agents 

 within moderate limits. At the same time it must be ob- 

 eerved that we have been far from stretching the known 

 facts ; for, when we compare the small extent of sea in 

 which any soundings can be found, with that of the vast 

 unfathomed ocean, it is obvious, that in assuming a depth 

 of one mile or two, we fall very short of the medium. M. de 

 3a Place, reasoning from the phenomena of the tides, states 

 it as highly probable that this medium is not less than eleven 

 English miles *. 



If a great part or the whole of the superincumbent mass 

 consisted, not of water, but of sand or clay, then the depth 

 requisite to produce these effects would be lessened in the 

 inverse ratio of the specific gravity. If the above-mentioned 

 occurrence took place under a mass composed of stone 

 firmly bound together by some previous operation of nature, 

 the power of the superincumbent mass, in opposing the 

 escape of carbonic acid, would be very much increased by 

 that union and by the stiffness or tenacity of the substance. 

 We have seen numberless examples of this power in the 

 course of these experiments, in which barrels, both of iron 

 and porcelain, whose thickness did not exceed one-fourth 

 of an inch, have exerted a force superior to the mere weight 

 of a mile of sea. Without supposing that the substance of 

 a rock could in any case act with the same advantage as 

 that of an uniform and connected barrel, it seems obvious 

 that a similar power must, in many cases, have been ex- 

 erted to a certain degree. 



We know of many calcareous masses which, at this mo- 

 ment, are exposed to a pressure more than sufficient to ac- 



* " On peutdonc reorder an moins conime txh» probable, que la profon- 

 f"«iir moyennc de la mer n'est pas au-dessous de quatre lieues." — De la Place, 

 l.ul. it I' Ac ad. liiuij. des Scutms, a mice 17 TO'. 



N 4 complish 



