No. IV.— O/e the Sol/atara of Pozzmli. 131 



flat plain so often mentioned, let us suppose to have been filled 

 up with a solid mass to the level of that truncation at the 

 period of the last eruption ; here we have every thing most 

 favourable to Mr Scrope's opinion. Now we would ask, 

 whence comes the vast bulk of mineral matter annually brought 

 to the surface ? We have it on the authority of Breislak, * 

 that he never found a vein, or even a particle, of sulphur in the 

 natural soil or crust of the Solfatara in the deepest pits he had 

 occasion to make ; and he shows that the whole sulphur of- 

 commerce is derived from the decomposition of the sulphu- 

 retted hydrogen gas, (the mode of which chemists have more 

 lately satisfactorily pointed out, as we shall explain shortly) 

 Now Sir William Hamilton -f* tells us that even in his time, 

 when the mode of working was confessedly imperfect and dila- 

 tory to the last degree, that 273 quintals, or near 30,000 En- 

 glish pounds of sulphur were annually prepared from the de- 

 posits of the " fumerolc." It therefore becomes a question, 

 whence the millions of pounds were drawn, which for centuries 

 have been deposited in this form ? The conclusion I conceive 

 is obvious, that this alone must have formed a chasm corre- 

 sponding to our ideas of magnitude, without any hypothetical 

 considerations whatever, but which, according to my ideas of 

 volcanic action, are equally tenable both in modern and extinct 

 craters. 



The disintegrated soil of the crater is in general unfavour- 

 able to the growth of plants, probably from the large quantity 

 of gaseous matter it contains, the abundance of sulphurous 

 acid, and the various acrid salts which it produces. It would 

 appear, however, that Ferber has been too hasty in his remark, 

 that the Arhutus unedo and Erica carnea are the sole possessors 

 of the soil. There are considerable spaces of vegetable soil in 

 which vegetation is luxuriant, such as the vine and chestnut 

 when planted, as indeed we might expect wherever the potash, 

 of the felspathose lavas in a state of disintegration is abundant. 

 The Erica and Spartium junceum succeed the lichens in such 

 spots. The arhutus and erica have indeed the appearance of 

 peculiar richness, especially the former, when covered with 



* Campmiie, ii. 120. 



f Campi Phlegrcei. Folio. Vol. ii. Explanation of Plate xx v. 



