DISAPPEARING OP RIVERS. 
009 
lYiiist be bollow quarries serving for strainers to these waters. He 
then enters into a discussion of this question : Are there any siibter- 
fanedus rivers, and is the proposition of some persons in favour of 
this particular, well founded? He makes it apparent, by several 
instances which be quotes, and by many reasons which he urges, 
that there are at least strong presumptions in favour of this opinion. 
A fact that is observed in the betoirs of the rivers, and particularly 
of the Rille, proves in some measure that there are considerable lakes 
of water in the mountains which limit its course : ^this fact is, that 
in winter the greatest part of thmr betoirs become springs, which 
supply anew the river’s channel with as much wafer as they had ab- 
sorbed from it during the summer. Now, whence can that water 
come, unless from the reservoirs or lakes that are enclosed in tlie 
mountains, which being lower than the river in summer, absorb its 
water, and being higher in winter by occasion of the rain they re- 
ceive, send it back again in their turn ? Mr. Guettard remarks, that 
this alternate effect of the betoirs swallowing up the water, and 
restoring it again, causes, perhaps, an invincible obstacle to the 
restraining of the Water within the channel of the river. It has indeed 
been several times attempted to stop these cavities ; but the water 
returns with such violence in winter, that it generally carries away 
the materials with which they were stopped. The Sap-Andre is lost 
in part, like the Ithone and the Rille, but there is something more 
remarkable in it than in these rivers ; viz. that at the extremity of its 
course, where there is no perceptible cavity, it is ingulfed, without 
any fall ; the water passes, between the pebbles, and it is impossible 
to foroe a slick into that placd any farther than into the betoirs. 
What makes this river take that subterranebus direction, is an impe- 
diment vvhichi in that place; it is there stopped 
by a rising ground, six or seven feet high, whose bottom it has very 
likely,; ipidermined, to gain a free passage, not having been able to 
make its way over it. At some distance it appears again; but in 
wdnter, as there is a greater quantity of water, it passes over that 
Eminence, and keeps an uninterrupted course. 'The Drome, after 
having lost some of its water in its course, vanishes near the pit of 
Soiicy in that place ; it meets with a sort of subterraneous cavity, 
nearly, tyyenty-five feet wide, and more than fifteen deep, where the 
river is in a manper stopped, and into which it enters, though without 
any perceptible motion, and never appears again. M. Guettard ob- 
serves, that in a part of Lorraine, which likewise is not very extensive, 
five other rivers lose themselves in the same manner. Mr. Guettard 
finishes Ibis memoir with some observations upon the Terre. This 
fiver is lost in the same manner as the Rille ; and though it is very 
near Paris, this singularity is unknown to almost every body : were 
it not for the account of the Abbe le Boeuf, M. Guettard would have 
been ignorant of it. 
We may add to these phenomena, that we have in Surrey the river 
Mole, which rises in Dorking hundred, and, after a considerable 
course, passes by Witchill, near Dorking ; a little beyond which, this 
river hides itself, or is swallowed up, in a caveirn at the foot of the 
hill, whence Camden says it is called the Swallovv ; he also takes 
4 H 
