352 iJintsfor the Formation cf 



27- To examine, in general, in the lavs, the nature of the 

 earth and Ron es of which it has been formed. 



37. A. T(^ ftudy the origin of the cryflals found inclofed 

 in the lava, as the white garnets or lencites in that of Vefu- 

 vius, in order to afcertain whether thefe cryftals have been 

 formed in the lava fince the time of its fufion, or whether 

 tJiey pre-exifted in the flones from which the lava was pro- 

 duced. 



28. The nature and progrefs of the decompofition of the 

 different kinds of lava, either by volcanic acids or meteors. 



28. A. Whether there are any which have actually been 

 ih fufion, and yet have prtTerved all the external characters 

 which the ftone had before it was fubjefted to the ailion of 

 tjie fubterranean fires. 



29. The origin of volcanic aflies, pozzolanas, tarras, 

 tufas, &c. 



30. The origin of pumice ftones : whether they are gra- 

 nites or feld-fpars, afbeftos, phrcnites, deodalites, or potter's 

 clay more >>r lefs ferruginous, or, laftly, the remains of the 

 decompofition of pit-coal. 



30. A. Whether, as M. de Fichtel believes, the adion 

 of the tire of volcanoes may augment the fufibility of fcld- 

 fpar, and change it, in the fame manner as quartz, into real 

 zeolite. 



3,1. Nature of the obfidlans or volcanic glafs : whether 

 tliey be really glafs, and the refults of a complete fufion ; or 

 whether they are not rather (lon(?s of a vitreous appearance, 

 and which have not been expofed to the aftion of a heat 

 fufficiently ftrong to fufc them. 



32. Whether there -exift ancient kinds of lava, which, as 

 related of thofe of Ifchia, are fufceptible of being heated by 

 the moifture of rain and fogs, which would fupport the con- 

 je6ture of No. 14. 



C. Obfervations to be made on Hills and Mountains which 

 are doubted to have been really Volcanoes. 



33. The form, elevation, and other dimcnfions of the hill 



or 



