( M5 ) 
If it be obje&ed, that fuch Ponds are fall for fome 
time, which a Tantalus cannot be, becaufe it begins 
to run out as foon as full j that may be eafily folv’d, 
by fu'ppofing the hidden Tantalus , (or intermediate Ca- 
vity between the River and Pond) to contain more Wa- 
ter than the vifible one, provided it does not contain fo 
much as not to be emptied, before the Return of the 
Tide. 
The fame Solution will ferve for wet and dry Sea- 
fons, only fuppofing the Cavities larger. 
If it be asked, where the Water of the vifible Tanta- 
lus , near a River, can run j it may be anfwer’d, that all 
this may happen, tho’ the fecond, or lowed Tantalus 
fhou’d have its Bottom higher than low Water-Mark 
in the River. And for the Syphons, which are of a 
particular Make in the Cup ; tho’ fuch be not fuppos’d 
in the Earth, yet any long PaiTage, rifing in the Middle, 
will anfwer the End. . See Fig. f. where ABCD re- 
prefents the Channel of a River, AD high Water-Mark, 
and GH low Water-Mark ; ZI a Palfage from the Ri- 
ver to the Cavity IKLMN, or firft, or hidden Tan - 
talus ^ L M Q, the Syphon of the firft Tantalus , run- 
ning into the fecond Tantalus , or vilible Pond O QJl P, 
which by its Syphon R S V runs out into low Grounds 
that may be above the low Water-Mark G H j and the 
Bottom KLof the firft Tantalus may be above the 
Top of the laft, whofe Level is the Line W W. 
A B C D Y O QJR. P V H is the Se&ion of the Surface 
of the Earth. 
Vol. XXXIII. 
X 
IV. FobiliJJmi 
