THE EAllTH. 45 



ness 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 caleinable 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 hai"d gray stone, four 

 of red sand streaked with white, three of white sand, and fifteen 

 of reddish \-itrifiable sand. " 



In this manner the earth is every where found in beds over 

 beds ; and, what is still remarkable, each of them, as far as it 

 extends, always maintains exactly the same thickness. It is 

 fomid also, that as we proceed to considerable depths, eveiy 

 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 are 

 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 interrupti'^n ; on the contrary, 

 they are ever at small intervals, cracked through as it were by 

 perpendicular fissures : the earth resembling, in thi.» 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 adventiti- 

 ous substances, that the rain, or some other accidental 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 gulph below. These amazing 

 clefts are well known to such as have passed these mountains, 

 where a chasm frequently presents itself several 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 

 ihen the spectator observes on each side friphtful precipices 



