VOL. XLI.J PHILOSOPHICAL TKANSACTIONS. 377 



On the 23d of June 1733, about Q in the evening, the inhabitants of the 

 village saw the walls of their houses shake sensibly ; on which they all withdrew 

 out of them, and saw that the hill visibly melted away, as it were, the greater 

 part of the land sliding along towards the vale; other parts subsided sensibly; in 

 some places the earth, opening, formed new gulls, and those that were there 

 before, grew much wider ; sometimes the ground which slid along in large 

 pieces, stopped, and tumbled one piece over another ; and the rocks, which 

 broke loose from that rolling earth, precipitated themselves into the valley, 

 which became quite filled up with them, as well as with the earth which rolled 

 down, by which the neighbouring road becaine impassable. 



All this was done very gently, and even sometimes almost imperceptibly ; a 

 sensible motion was observed during the space of 3 or 4 days at different times; 

 one house even did not fall till the 10th of July. During all that time no noise 

 was heard, any otherwise than what proceeded from the rocks falling into the 

 valley, and from some large masses of earth, which loosening themselves from 

 the steeper parts, fell down with precipitation. By this rolling were carried 

 away 26 buildings, some of which subsided with the ground, and, being shaken 

 at their foundations, tumbled on a heap ; the remains of some others appear 

 yet, on those pieces of ground that rolled down into the valley. It is com- 

 puted, that the ground which slid away, or was lost by being buried under the 

 rubbish of the others, amount to the number of 150 acres of Paris measure. 

 It is observable, that in this number were comprised several orchards, besides 

 that the whole ground was covered with trees, either walnut-trees on the hill, 

 or willows and poplars in the valley, about 4000 in all. 



If one may conjecture what was the cause of so dismal an accident, it seems 

 it proceeded from the situation of the ground, and the nature of the soil. The 

 first surface of the hill, about 4 or 6 feet deep, was a pretty light earth, easily 

 dried by the heat of the sun ; under this first layer there was a stratum of fat 

 clay, which at present lies open in several places, and which is very moist, so 

 that the water is seen bubbling out of it in some places. 



The great rains that fell in the beginning of the spring, soaked through and 

 diluted this stratum of clay, which retained and gathered all the waters of tlie 

 hill running between the two layers ; the heat of the summer ensued, which 

 dried up the upper surface, and formed it into a sort of solid crust, which rest- 

 ing on a fat and moist clay, and by its steep situation being inclined to slide to- 

 wards the valley, its whole surface loosened itself by great pieces, and break- 

 ing in several places, slid along towards the place whither its declivity would 

 naturally carry it. There are some parts which moved almost insensibly, and 

 only sunk or subsided, either because the rolling of the neighbouring soils made 



VOL. VIII. 3 C 



