( 3*1 ) 
is large ; for in this Cafe, the Air-Bubbles, made by 
the Fall of the Feeding-Stream from O to the Bottom 
of the Cavern, will fometimes accidentally get into the 
Mouth of the Syphon at M, and lodging at N, will fo 
choak it as to render its running and flopping, as well 
as the Quantity of its Difcharge, entirely uncertain j 
fo that thefe fort of Fountains will admit of no far- 
ther Confideration. 
But before I leave the Confideration of Fountains ex- 
plicable by oneRefervoir and Syphon, it may not beamifs 
to obferve, that thofe which intermit regularly will 
have their Flux always longer, and their Paufe orln- 
rermiflion Ihorter in Winter and in wet Weather, than 
in Summer or in a dry Seafon ; which is a Confe- 
quence of this Hypothefis, by which it may be exa- 
mined, whether it bq applicable to any particular inter- 
mitting Fountain, or not. 
If the (ingle Refervoir and Syphon has another Out- 
let at R, Fig. i.fituated between the Bottom C D of the 
Cavern, and the Top' of the Syphon N, we (hall have 
another kind of Fountains. For if the Feeding-Stream 
at O, is capable of being difcharged by the Out-let at 
R, a Fountain derived from R will continually run, 
whilft the Feeding-Stream can be difcharged that Way, 
and will encreafe and decreafe with any little Altera- 
tion happening to the Feeding-Stream at O, provided 
that the faid Stream does not grow too large for the 
Out-let at R. But in that Cafe the Cavern muft be 
filled uptoN,andtheSyphonmaybeginto play; which, 
together with the Out-let at R,may difcharge fo much 
as to make the Surface of the Water in the Cavern 
fink below R, and confequently the Fountain proceed- 
ing from R muft flop. If the Difcharge of the Syphon 
is fo great as to empty the Cavern, then the Fountain: 
derived 
