476 DOMAIN XII. VOLCANIC. 



La Cavalleria, is worthy of attention. Under a 

 uniform bed, from 15 to QO feet in thickness, the 



in strata, lava is found divided into strata of from three to 

 four feet : these divisions are formed by parallel 

 and horizontal lines, and where these are dug 

 down to, the lava is found to have separated itself 

 spontaneously into beds. Below them are large 



Prisms, prisms, commonly hexagonal, which are disjoined 

 with great ease: in some places these prisms, 

 instead of the lower are found in the upper part 

 of the current. Some of these large prisms I 

 have seen, the summit of which was parted into 

 a number of small prisms. These observations 

 sufficiently demonstrate that the recession of the 

 matter of the lava, when in the act of cooling, 

 is the sole cause of the form, whether even or 

 prismatic, which it assumes ; and that this cause 

 is capable of giving to lava the appearance of 

 stratification. This phenomenon may afford 

 ground for reflection to those geologists who so 

 strongly insist on the fact of horizontal and ver- 

 tical beds of granite, as affording a proof of 

 deposits being first made in a fluid, and after- 

 wards diverted from their pristine position. I 

 am far from inclining as yet to adopt any ge*-- 

 ological system whatever; for, in my opinion, 

 we have not hitherto collected a sufficient num- 

 ber of facts to produce one that will bear the 



