Strictures on Volcanos and Earthquakes. 5 1 



Art. VIII. — Strictures on the Hypothesis of Mr. Joseph Du 

 Commun^ on Volcanos and Earthquakes ;* by Benjamin 

 Bell, of Charlestown, Mass. 



TO MR. JOSEPH DU COMMUN. 



Sir — In accordance with your opinion, as well as witii 

 that of Dr. Franklin, Mr. Perkins and others — I will allow 

 that atmospheric air can be compressed to such a degree as 

 to be heavier than water ; and that if forced down by means 

 of a bell lower than twenty five thousand six hundred feet 

 below the surface of the sea, it may stay there, for the present, 

 or may fall to the bottom. We will suppose the lowest 

 depth of the sea-water to be found at the precise point of 

 twenty five thousand six hundred feet from the surface, 

 which, for brevity, I shall call the separating point; and that 

 a stratum of condensed air occupies the space between that 

 point and the liquid oxygen below, a gallon of which stratum 

 being heavier than a gallon of sea-water. At this point of 

 contact (separating point) the air (see page 16, line 30) must 

 be, as you say, "exactly of the same density with the water." 



But what would be the density of a bubble of air, if con- 

 veyed by the bell and left one foot above the separating point? 

 As this bubble would have a density less than the air at the 

 separating point, it must rise to the surface ; it cannot fall, 

 or, as you say, " shower through the water." 



If then a bubble of air rises, when formed or left one foot 

 above the separating point, it may be fairly asserted that it 

 would rise if formed one inch, or even yi^ of an inch above 

 it. To maintain this gaseous stratum then, it is necessary 

 to suppose, that the evolution of gas from the water is made 

 precisely at the separating point, and that air bubbles (i. e. 

 air surrounded by a liquid) are not formed. 



But what should cause a separation at all? The air held 

 in solution near the separating point ought to be combined 

 with some degree of force, else it would be likely to separ- 

 ate before it was carried there. Supposing however, that 

 it arrives down to the point, there is a great objection to its 

 separating at that precise point, in preference to a quarter 

 of an inch above ; for no chemical attraction between the 



* See Vol. XV. No. 1. Art. iii. of this Journal. 



