446 



DISTRIBUTION OF PLANTS. 



accumulation of fragments spattered over. The large lake was now 

 overflowing in two or three places ; the pouring lava moving onwards 

 regularly but very slowly. 



Continuing Southward as far as yesterday's route, to complete the 

 circuit of the " black ledge ;" we next ascended the slope to the plain 

 above, and turned Westward ; but a wall-like cliff compelled us to re- 

 cede nearly a mile from the Great Crater, before the ascent became 

 practicable. After ascending a second low cliff or ledge, we came upon 

 the Southwestern portion of the great Crevice of formation and erup- 

 tion : traceable by parallel gaping fissures ; and marked in the distance 

 by columns of rising steam, extending in a line for many miles towards 

 the sea. 



These fissures are filled at intervals with gravel and sand from the 

 surrounding plain, blown in by the winds; the accumulations, where 

 rising to the surface, affording a passage across. After becoming 

 familiar with these crossing-places, I was about stepping on one ; but 

 by a sudden efibrt recovered my foothold, for my staff penetrated the 

 ground. On further examination, the staff" passed its whole length 

 downwards without obstruction; and it was now perceived, that in 

 place of sand and gravel, the crevice was here filled with jjz<>;i/ce; we 

 were obliged therefore to seek another crossing-place. The tract 

 covered with pumice commences along these fissures ; and for the next 

 mile we found the layer of bits of pumice from three inches to a foot 

 deep. On another occasion, in passing around at the distance of two 

 miles from the Great Crater, I first fell in with bits of pumice, when 

 the smoke-like vapor from the lake bore North-northwest ; but the 

 bits were thinly scattered, and continued rare until I reached the 

 Crevice of formation and eruption. It was thus ascertained, that 

 the tract of pumice lies immediately under the cloud of smoke-like 

 vapor; which, from the constant direction of the wind, is always 

 moving in one direction. The pumice of the Great Crater resembles 

 bits of dry sponge, and seemed of a lighter kind than that usually found 

 in cabinets : in securing Specimens, it is necessary to guard against 

 their being blown away by the wind ; and in fact, the layer on the 

 plain seemed to be chiefly kept down by the mixture of sand and 

 gravel. Once, while looking down at night upon the molten lake, 

 two or three small fiery masses were ejected from the illuminated lines 

 between the seeming floes ; masses light enough to be afterwards 

 whirled about by the wind : I supposed, at the time, that this might 



