THE EARTH. 



17 



deeper, and view the earth cut perpendicu- 

 larly downwards, either in the banks of great 

 rivers, or sleepy sea-shores, or, going still 

 deeper, if we observe it in quarries or mines, 

 we shill find its layers regularly disposed in 

 their proper order. We must not expect, 

 however, to find them of the same kind or 

 thickness in every place, as they diiler in dif- 

 ferent soils and situations. Sometimes marl 

 is seen to be over sand, and sometimes under 

 it. The most common disposition is, that 

 under the first earth is found gravel or sand, 

 then clay or marl, then chalk or coal, marbles, 

 ores, sands, gravels; and thus an alternation 

 of these substances, each growing more dense 

 as it sinks deeper. The clay, for instance, 

 found at the depth of a hundred feet, is usually 

 more heavy than that found not far from the 

 surface. In a well which was dug at Amster- 

 dam, to the depth of two hundred and thirty 

 feet, the following substances were found in 

 succession:" seven feet of vegetable earth, 

 nine of turf, nine of soft clay, eight of sand, 

 four of earth, ten of clay, four of earth, 

 ten of sand, two of clay, four of white sand, 

 one of soft earth, fourteen of sand, eight 

 of clay mixed with sand, four of sea-sand 

 mixed with shells, then a hundred and 

 two feet of soft clay, and then thirty-one feet 

 of sand. 



In a well dug at Marly, to the depth of a 

 hundred feet, Mr. BufFon gives us a still more 

 exact enumeration of its layers of earth. 

 " Thirteen of a reddish gravel, two of gravel 

 mingled with a vitrifiable sand, three of mud 

 or slime, two of marl, four of marly stone, 

 five of marl in dust mixed with vitrifiable sand, 

 six of very fine vitrifiable sand, three of earthy 

 marl, three of hard marl, one of gravel, one of 

 eglantine, a stone of the hardness and grain of 

 marble, one of gravelly marl, one of stony 

 marl, one of a coarser kind of stony marl, two 

 of a coarser kind still, one of vitrifiable sand 

 mixed with fossil-shells, two of fine gravel, 

 three of stony marl, one of coarse powdered 

 marl, one of stone calcinable like marble, 

 three of gray sand, two of white sand, one of 

 red sand streaked with white, eight of gray 

 sand with shells, three of very fine sand, three 

 of a hard gray stone, four of red sand streaked 



Varenius, as quoted by Mr. Buffon, p. 



with white, three of white sand, and fifteen of 

 reddish vitrifiable sand. 



In this manner the earth is every where 

 found in beds over beds; and, what is still re 

 markable, each of them, as far as it extends 

 always maintains exactly the same thickness 

 It is found also, that as we proceed to con- 

 siderable depths, every layer grows thicker. 

 Thus in the adduced instances we might have 

 observed, that the last layer was fifteen feet 

 thick, while most of the others were not above 

 eight ; and this might have gone much deeper, 

 for aught we can tell, as before they got 

 through it the workmen ceased digging 



These layers are sometimes very extensive, 

 and often arc found to spread over a space of 

 some leagues in circumference. But it must not 

 be supposed that they are uniformly continued 

 over the whole globe without any interruption: 

 on the contrary, they are ever, at small intervals, 

 cracked through as it were by perpendicular 

 fissures ; the earth resembling, in this respect, 

 the muddy bottom of a pond, from whence the 

 water has been dried off by the sun, and thus 

 gaping in several chinks, which descend in a 

 direction perpendicular to its surface. These 

 fissures are many times found empty, but 

 oftener closed up with adventitious sub- 

 stances, that the rain, or some other acci- 

 dental causes, have conveyed to fill their 

 cavities. Their openings are not less different 

 than their contents, some being not above half 

 an inch wide, some a foot, and some several 

 hundred yards asunder ; which last form those 

 dreadful chasms that are to be found in the 

 Alps, at the edge of which the traveller stands 

 dreading to look down at the immeasurable 

 gulf below. These amazing clefts are well 

 known to such as havepassed thesemountains, 

 where a chasm frequently presents itself se- 

 veral hundred feet deep, and as many over, 

 at the edge of which the way lies. It often 

 happens also, that the road leads along the 

 bottom, and then the spectator observes on 

 each side frightful precipices several hundred 

 yards above him; the sides of which corres- 

 pond so exactly with each other, that they 

 evidently seem torn asunder. 



But these chasms, to be found in the Alps, 

 are nothing to what Ovalle tells us are to be 

 seen in the Andes. These amazing moun- 

 tains, in comparison of which the former are 



