321 Artificial Volcano. [Book VI. 



the internal parts of the earth abound much in this 

 metal. 



The origin of thefe fubterraneous fires is not enfily 

 explained. Iron filings mixed with powdered ful- 

 phur, and the whole moiftened with water into a pafte, 

 \ve have formerly feen, will fvvell, become hot, and, 

 if the quantity is confiderable, will throw out a blue 

 flame. It is a mixture of this kind which is ufed for 

 making an artificial earthquake, for fiich a quantity of 

 inflammable gas is produced during the fermentation, 

 that if the mafs is buried in the earth, the gas will 

 force a paflage for its efcape, and exhibit, on a fmall 

 fcale, the phenomena of an earthquake. M. Lemery 

 feems to have been the firft perfon who iiluftrated, in 

 this manner, the origin of volcanic fires and earth- 

 quakes. ,He mixed twenty-five pounds of iron filings 

 with an equal weight of fulphur, and having made 

 them into a pafte with the addition of water, he put 

 them into a pot, covered them with, a cloth, and bu- 

 ried them a foot under ground. In about eight or 

 nine hours time the earth fwelled, became warm, and 

 cracked, and hot fulphureous vapours were per- 

 ceived*. Now, large beds of martial pyrites, which 



are 



.* That part of this experiment (fays Bifhop Watfon) which 

 relates to the production of fire, by the fermentation of iron filings 

 and fulphur when made into a pafte, has been frequently repeated 

 fince the Time cf Mr. Lemery. I myfelf have made it more than 

 once, but I have nothing material to add to his account, except 

 that the flame, when the experiment is made in the open air, is of 

 very {hort duration ; and that the whole mafs, after the extinction 

 of the flame, continues at intervals, for a longer or (horter time, 

 according to its quantity, to throw out frarks; and that a ladle 

 full of the ignited mafs,, being dropped down from a confiderable 

 height, dfcfcends like a mower of red- hot afhes, much refembling ' 

 the paintings of the eruptions of Mount Vefuvius, which may be 

 .icen at the Britifh Mufeum. It has been obferved, that large 



quantitioi 



