Notice of Active and Extinct Volcanos. 83 



out for a considerable time sufficient heat to the adjoining" strata, 

 to place the sulphur at the temperature necessary to cause its 

 combination with oxygen; hence a certain portion of sulphurous 

 acid would be continually emitted, which however would be soon 

 decomposed by the hepatic gas present. The water resulting 

 from this process would percolate into the recesses of the rock, 

 act upon any portions of the alkaline and earthy metalloids that 

 might have escaped the original action, and give birth to a 

 fresh volume of hydrogen gas, ready in its turn to dissolve anew 

 portion of sulphur, and thereby to contribute to the repetition of 

 the same phenomena. 



"The separation of muriatic acid from the common salt pre- 

 sent in sea water is explained, on the common principles of chem- 

 istry, by the superior affinity exerted by the base for the siliceous, 

 or aluminous earth than for the acid, and the sublimation of iron 

 in the state of fer oligiste, rather than of peroxide, may re- 

 sult from the deoxydizing property of the sulphuretted hydro- 

 gen at the same time disengaged. The carbonic acid given off 

 may be derived either from the carbonaceous matters that have 

 entered into combustion, a view of the subject which is perhaps 

 favored by the phenomena ofthepietra mala, or from the action 

 of the high temperature upon the carbonates of lime and magne- 

 sia, existing in the strata above the seat of the volcanic action. 

 I have already remarked, that this latter gas is chiefly found in 

 volcanos that have become extinct, or have been long in activitj r , 

 where time appears to have been given for the heat to extend it- 

 self beyond the immediate sphere of the volcanic action. 



" In short, on the supposition of salt water and air being brought 

 in contact with the sulphurets of the metals and earthy metalloids, 

 all the known phenomena of volcanos may be deduced in the or- 

 der in which they appear to occur: in the first place, so long as 

 air was present, an evolution of large volumes of muriatic, sul- 

 phurous, and nitrogen gases, together with aqueous vapor, would 

 take place ; at a later period, when the oxygen was expended, 

 sulphuretted hydrogen and carbonic acid, with a smaller quantity 

 of muriatic acid, would appear; lastly, when all the other ef- 

 fects had subsided, aqueous vapor and carbonic acid might contin- 

 ue to be evolved." 



The discussions which occupy the greater part of the last 

 forty pages of Professor Daubeny's work must be studied in 

 detail, in order to be intelligible, and they cannot be so in 

 any event, except to geologists of considerable attainments. 

 They relate chiefly to the following topics, namely, 



1, To the analogies between volcanic and trap rocks. 



