226 



THE CABINET OF NATURAL HISTORY 



with rain, they might have given rise to the stratum of 

 black clay which is described as covering the lava. The 

 small conical mounds (called "hornitos" or ovens) may 

 resemble those five or six small hillocks which existed in 

 1823, on the Vesuvian lava, and sent forth columns of va- 

 pour, having been produced by the disengagement of elastic 

 fluids heaving up small dome-shaped masses of lava. The 

 fissures mentioned by Humboldt as of frequent occurrence, 

 are such as might naturally accompany the consolidation of 

 a thick bed of lava, contracting as it congeals; and the 

 disappearance of rivers is the usual result of the occupation 

 of the lower part of a valley or plain by lava, of which there 

 are many beautiful examples in the old lava-currents of 

 Auvergne. The heat of the '< hornitos" is stated to have 

 diminished from the first, and Mr. Bullock, who visited 

 the spot many years after Humboldt, found the temperature 

 of the hot spring very low, a fact which seems clearly to 

 indicate the gradual congelation of a subjacent bed of lava, 

 which, from its immense thickness, may have been enabled 

 to retain its heat for half a century. 



Another argument adduced in support of the theory of 

 inflation from below, was the hollow sound made by the steps 

 of a horse upon the plain, which, however, proves nothing 

 more than that the materials of which the convex mass is 

 composed are light and porous. The sound called " rim- 

 bombo" by the Italians, is very commonly returned by 

 made groxmd, when struck sharply, and has been observed 

 not only on the sides of Vesuvius and other volcanic cones 

 where there is a cavity below, but in plains such as the 

 Campagna di Roma, composed in great measure of tufi"and 

 porous volcanic rocks. The reverberation, however, may, 

 perhaps, be assisted by groitos and caverns, for these may 

 be as numerous in the lavas of Jorullo, as in many of those 

 of iElna: but their existence would lend no countenance to 

 the hypothesis of a great arched cavity, or bubble, four 

 square miles in extent, and in the centre five hundred and 

 fifty feet high. A subsequent eruption of Jorullo happened 

 in 1S19, accompanied by an earthquake; but unfortunately 

 no European travellers have since visited the spot, and 

 the only facts hitherto known are that ashes fell at the 

 city of Guanaxualo, which is distant about one hundred and 

 forty English miles from Jorullo, in such quantities as to 

 lie six inches deep in the streets,and the tower of the cathe- 

 dral of Guadalaxara was thrown down, Lyell. 



BLACK GROUSE. 



The Black Grouse, black game, or black cock, (tetrao 

 tetrix,^ though inferior in size to the cock of the woods, is 



still a bird of considerable dimensions, being much larger 

 than the red grouse; and when full-grown, larger than the 

 pheasant. The black cock is a very handsome bird; the 

 general colour is black, but it is irridescent, and in certain 

 positions of the light shows a very fine purple. The tail is 

 very much forked, the outside feathers curled, and the 

 lower part, towards the base, white. Upon the throat there 

 is a kind of down, but no long or regularly-formed feathers. 

 The length of the male bird is about twenty-eight inches, 

 and the extent of the wings nearly three feet; and the weight 

 between three and four pounds. The female is a much 

 smaller bird, and has not the curled feathers in the tail. 



Though the places at which the Black Grouse is found are 

 not quite so elevated — so near to the summits of the moun- 

 tains as the habitations of the ptarmigan — it is a bird fond of 

 wild and secluded spots; and its numbers in these islands 

 are very fast declining. What with improvements of land, 

 and improvements in the arts of its destruction, it is not 

 nearly so abundant in England as it was formerly; though 

 it be still met with in the more elevated and secluded places 

 in the south of England, in Staffordshire, in North Wales, 

 and generally where there are high and lonely moors. In 

 the Alpine parts of Scotland it is more abundant, though 

 the introduction of sheep, generally, upon the mountains, 

 is said to be diminishing the numbers. The black cocks 

 are more frequently found in the woods than the red grouse, 

 though the moors, with a difierence of elevation, be the 

 favorite abodes of both. Their food is also similar; consist- 

 ing of mountain-berries, the tops of heath, and the buds of 

 pine and other Alpine trees. Though they seek their food 

 in the open places during the day, they, where they have 

 the accommodation of trees, perch during the night like 

 pheasants. It is chiefly during the winter months, how- 

 ever, and the early parts of spring, when all food, save the 

 tops of the pines, is hidden under the snow, that they do 

 that; for when the breeding season commences, they assem- 

 ble on the tops of the mountains and highest parts of the 

 moors, but never higher than they can find heath ; the young 

 shoots and embryo blossoms of which are at that time their 

 principal food. 



Some parts of their character resemble that of common 

 poultry. They do not pair; but when the breeding season 

 commences, the cocks ascend to the tops of the mountains, 

 and clap their wings and crow; to which call the females an- 

 swer, by making their appearance, and uttering a sort of 

 clucking sound. War immediately ensues among the 

 males, as each is anxious to have in his train as many 

 females as possible. Their heels are armed with spurs: 

 Iheir mode of fighting is the same as that of game-cocks, 

 and they enter upon the strife with the same devotedness. 

 Although upon other occasions they are among the shyest of 



