506 Hot Springs in Iceland. [Book VII. 



depofits .filiceous earth ; and that of this very matter 

 it has formed for itfeif a crater, in which columns of 

 water, of a fiupendous bulk, after they have been 

 thrown to the height of ninety feet and upwards, 

 fall, and are again received. The heat of the water 

 during the explofion cannot be meafuredj but after 

 it has riien and fallen through a ftratum of air ninety 

 feet thick, it raifes the thermometer to 212, which 

 evinces that the heat in the bowels of the earth muft 

 be much more intenfe ; and at this we mall cea'e to 

 wonder when we confider, that in this cafe the fub- 

 terraneous fire acts upon the water in caverns, clofed 

 up by very thick ftrata of ftones, an apparatus far more 

 effective than Papin's digefter. The crater was at 

 firft undoubtedly formed, and is daily ftrengthened by 

 filiceous earth, which quits the menftruum on its being 

 cooled, falls down, and, being in fomewhat like a foft 

 flate, concretes *. 



About fixty yards from the fhore of the ifland of 

 Ifchia, at a place called St. Angelo, a column of 

 boiling water bubbles on the furface of the fea with 

 great force, and communicates its heat to the water 

 of the fea near it. It boils winter and fummer, and 

 is of grea^t ufe to the inhabitants in bending their 

 planks for (hip-building, &c. The fifhermen alfo 

 frequently, employ this curious caldron to boil their 

 fiih. Near the more of this ifland Sir William 

 Hamilton found, when bathing in the fea, many fpots 

 where the fand was fo intenfely hot under his feet as 

 to oblige him haflily to retire. 



There is alfo a boiling fpring near Viterbo, in 

 the Roman Hate, called the Builicame. It is a cir- 

 cular pool of about fixty feet in diameter, and ex- 



* 'Bergman's Differt. 13, 



ceedingly 



