Observations on Volcanoes and their Lava, 267 



before my eyes, was that of an ebullition, accompanied 

 with inflamraable vapours, and the gerbes of burning mat- 

 ters which ihcv threw up at intervals were separated pieces 

 of the lava in its state of fusion. I saw several of them in 

 the air chanse their form, and sometimes become flat on 

 the bodies which they struck or embraced in falling. And 

 among the most apparent of these fragments there are al- 

 ways a multitude of small ones of the size of peas and nuts, 

 and still smaller ones, which show at their surface, by their 

 asperities, all the characters of laceration. 



The name of scorice has been given to these fragments to 

 distinguish them from compact lava, though their compo- 

 sition be the same as that of the hardest lava ; and it is for 

 want of reflecting properly on this point that it has been 

 said that it is the compact part only that we must observe, 

 in order to judaic of their nature. The pieces which I took 

 from the flowing lava with an iron hook, have at their sur- 

 face the same lacerations and the same asperities as the frag- 

 ments thrown up by explosions, and both contain the same 

 substances. 



This separation, by tearing off the parcels of the lava 

 effected by fermentations and explosions which proceed 

 from their bosom, serves to explain those colunms, some- 

 times prodigious, of volcanic sand which rise from the 

 principal crater. When seen with a magnifying glass, this 

 sand exhibits nothing but lava reduced very small, the par- 

 ticles of which, rough with inequalities, liave the bright 

 black colour and the varnish of recent lava. 



Parcels of substances which exist in our strata, such as 

 fragments of quarlz, scales of mica, and crystals of feld- 

 spar, are found sometimes in lava. Similar matters must 

 no doubt be disseminated in the composition of our globe, 

 without there being reason to conclude that the strata 

 from which they proceed are the same as the exterior strata. 

 It is neither in the oranites, the porphyries, nor the horn 

 rock, and still less in the schists and calcareous rocks that 

 the schorls of volcanoes, the leucites, and perhaps olivins, 

 will be found. These small crystals are brought to view by 

 the lava, otherwise they would be unknown to us. 

 , These lavas contain a great deal of iron, which they ac- 

 quire neither from the granite nor porphyries. Might not 

 one see in the ferruginous sand which is found in abun- 

 dance on the borders of the sea near Naples, and in ihc 

 environs of Rome, specimens of that kind of pulverulent 

 strata from which lava proceeds ? 



1 have here offered enough to prove that it cannot be 

 determined 



