1859.] SCEOPE — COKES AND CRATERS. 509 



appearing to be composed, outwardly at least, of a black indurated 

 clay, or earthy "decomposed basalt" (for M. de Humboldt seems 

 rather doubtful what to call it) having a globular concretionary and 

 concentric lamellar structure ; and these small protuberances, as 

 well as the large conical hills, and the entire convexity of the 

 Malpais, are alike considered by him as so many hollow inflated blis- 

 ters (see figs. 1, 2, and 3). These appearances so explained, he rightly 

 calls, in his recent volume of ^Kosmos,' " The greatest, and, since my 

 American journey, the most celebrated phenomenon of volcanic up- 

 heaval." I believe this to have been also the j^rst statement ever 

 announced to the world of such a phenomenon, with the exception 

 of that (to which M. de Humboldt is never tired of referring as an 

 authoritative example) in the ^Metamorphoses' of Ovid, who vaguely 

 reports a tradition of something similar having occurred at Methone 

 in Greece *. 



While engaged, many years back, upon my work on Yolcanos, 

 which was published in 1825, I was so struck with the discord- 

 ance of M. de Humboldt's theory of the eruption of Jorullo with 

 the then-known ordinary laws of volcanic action, that I was led to 

 institute a close examination of the facts and relations respecting 

 this celebrated event, upon which his view of its origin was 

 grounded. And in the appendix to that work I showed in detail 

 (and I venture to think conclusively) that the theory is not at all 

 warranted by either class of evidence ; on the contrary, that both 

 the relation of the phenomena that accompanied the eruption, as 

 given by M. de Humboldt himself from the reports of eye-witnesses, 

 and its results as observed and described by him, are perfectly con- 

 sistent with the usual course of proceeding of an ordinary volcanic 

 eruption, witnessed in numberless examples in other parts of the 

 globe ; that the six conical hills are common eruptive cones of scoriae, 

 ashes, and other fragmentary matters (of which prodigious quantities 

 are stated in every account to have been thrown up from these 

 several points of the original plain f, at the commencement of the 

 eruption and throughout many subsequent months) ; that the con- 

 vexity of the " Malpais" surrounding these cones is (like aU the 

 other *' Malpais" of Spanish America) but the surface of a thick bed 

 of imperfectly liquid basaltic lava, which, having been poured out of 

 these vents in great abundance upon a flat plain, naturally accumu- 

 lated there around their base (its greatest height above the original 

 plain being only 470 feet, therefore not thicker than some of the 

 lava-streams of Iceland), and this at the foot of the great cone of 

 Jorullo, from which is yet seen descending into and joining the 

 " Malpais" a very bulky promontory of coarse-grained lava, by which 

 M. de Humboldt chmbed up to the crater ; finally, that the myste- 

 rious, but really insignificant, " hornitos" (which, by the later account 

 of Mr. Burkart, seem to have very soon disappeared, their covering 

 being washed away by the rains) were merely the higher superficial 



* " Extentam tumefecit humum, ceu spiritus oris 

 Tendere vesicam solet." — Ovid, ' Met.' lib. xv. 

 t Jorullo, the largest, is 1200 feet high from the plain. 

 VOL. XV. — PART I. 2 



