376 Scientific Intelligence. 



less frequented than the other pass. On the 1st of March, while approach- 

 ing towards the chain in which is situated the pass of the Portillo, we 

 were enveloped for upwards of two hours in a shower of ashes, which, on 

 further inquiry, I found proceeded from a volcano which had exploded 

 ahout two hours before, towards the centre of the Cordilleras. Owing to a 

 pretty strong breeze, I was only able to collect a very small quantity of 

 these ashes, but sufficient to identify it with some ashes which I had pre- 

 viously, on two occasions, collected at Mendoza, a distance of from 40 to 

 50 leagues from the volcano, which is situated near the pass of the Peu- 

 queues. This volcano has been very active during the last year, and in- 

 deed, ever since the great earthquake which destroyed Valparaiso a few 

 years ago. — Extract of a letter from Br Gillies to W. C. Trevelyan, Esq. 

 dated Mendoza, 11th April 1826. 



30. Singular Cascade of Lava. — Near Keokoa Mr Ellis observed a 

 curious phenomenon. Jt consisted of a covered avenue, of considerable ex- 

 tent, from 50 to 60 feet high, formed by the lava's having flowed over the 

 edge of a perpendicular pile of very ancient lava, from 60 to 70 feet high. 

 It appeared as if, at first, it had flowed over in one vast sheet, but had af- 

 terwards fallen more slowly, and in detached semifluid masses. These, 

 cooling as they fell, had hardened, and formed a pile, which, by a conti- 

 nued augmentation from above, had ultimately reached the top, and unit- 

 ed with the liquid lava there. It was evident that the lava had still con- 

 tinued to flow along the outside of the arch thus formed into the plain 

 below, as we observed in several places the courses of unbroken streams, 

 from the top of the cliff to the bed of smooth lava that covered the beach 

 for several miles. The space at the bottom between the ancient rocks 

 and more recently formed lava, was from 6 to 12 feet. On one side the lava 

 was perpendicular and smooth, showing distinctly the different and vari- 

 ously coloured masses of ancient lava of which it was composed, some of a 

 bright scarlet, others brown and purple. The whole pile appeared to have 

 undergone, since its formation, the effects of violent heat. The cracks and 

 hollows horizontally between the different strata, or obliquely through 

 them, were filled with lava of a florid red colour, and much less porous 

 than the general mass. This last bed of lava must have been brought to 

 a state of the most perfect liquefaction, as it had filled up every crevice 

 that was more than half an inch wide. It appeared highly glazed, and in 

 some places we could discover small round pebbles from the size of a hazel 

 nut to that of a hen's egg, of the same colour, and having the same vi- 

 treous covering, yet seeming to have remained solid, while the liquid lava 

 with which they were mixed had been forced by subterranean fire into all 

 the fissures of the ancient rock. 



The pile on the other side, formed by the dropping of the liquid lava 

 from the upper edge of the rocks, presented a striking contrast, but not a less 

 interesting sight. It was generally of a dark purple, or jet black colour, glit- 

 tering in the sun's rays, as if glazed over with a beautiful vitreous varnish. 



On breaking off any fragments we found them very porous, and con- 

 siderably lighter than the ancient lava on the other side. Its varied forms 

 baffled description, and were equal to the conceptions of the most fertile 



