MODIFIED by COMPRESSION. 163 



that at the bottom of a Tea, which would be founded by a 

 line much lefs "than double of the ufual length, and lefs than 

 half the depth of that founded by Lord Mulgrave, lime- 

 flone might be formed by heat ', and that, at the depth reach- 

 ed by Captain Ellis, the entire fufion would be accomplifh- 

 ed, if the bed of fhells were touched by a lava at the extre- 

 mity of its courfe, when its heat was loweft. Were the heat 

 of the lava greater, a greater depth of fea would, of courfe, be 

 requifite to conflrain the carbonic acid effectually ; and future 

 experiments may determine what depth is required to co-ope- 

 rate with any given temperature. It is enough for our prefent 

 purpofe to have fhewn, that the refult is poffible in any cafe, 

 and to have circumfcribed the neceffary force of thefe agents 

 within moderate limits. At the fame time it mud be obferved, 

 that we have been far from flretching the known fads; for when 

 we compare the fmall extent of fea in which any foundings 

 can be found, with that of the vaft unfathomed ocean, it is ob- 

 vious, that in affuming a depth of one mile or two, we fall 

 very fhort of the medium. M. de la Place, reafoning 

 from the phenomena of the tides, flates it as highly probable 

 that this medium is not lefs than eleven Englifh miles *. 



If a great part or the whole of the fuperincumbent mafs 

 confifted, not of water, but of fand or clay, then the depth re- 

 quifite to produce thefe effects would be leflened, in the inverfe 

 ratio of the fpecific gravity. If the above-mentioned oc- 

 currence took place under a mafs compofed of Hone firmly 

 bound together by fome previous operation of nature, the 

 power of the fuperincumbent mafs, in oppofing the efcape of 



X 2 carbonic 



* " On peut done regarder au moins comme tres probable, que la profondeur 

 " moyenne de la mer n'eft pas au-deflbus de quatre lieues." De la Place, 

 Hijl. de V.Acad. Roy. des Sciences, annee 1776. 



