( 3to ) 
to known. For if the Feeding-Stream at O fhould 
arife only from the Rains in Winter, or from the melt- 
ing of the Snow in Summer, the intermitting Fountain 
would become a temporary Spring, as Y)r.Plot calls fuch 
Springs which are confined to a Seafon. Or if the 
Feeding-Stream at O fhould be conftant, but yet liable 
with other Springs to anEncreafe and Decreafe arifing 
from the Seafons, Weather, or other Caufes, the 
Conftruction of the Syphon would make a great Alter- 
ation. For when the Syphon is fo made, that its Dif- 
charge (which is continually decreafing, as the Surface 
of the Water fubfides in the Cavern) (hall at any Time 
be equal to the Feeding-Stream entering at 0,in fuch a 
Cafe, the Syphon muft continually run, and yet not 
empty the Cavern, ’till the Feeding-Stream at O isfuf- 
liciently diminifhed. But, when the Diameter of the 
Syphon at N, according to the Height of the Cavern, 
is fo great, and the Feeding- Stream at O fo fmall, that 
the Syphon can carry off (in the Manner of a Wafte- 
Pipe) all the Water which comes in, and yet not run 
with a full Stream } the Syphon muft then continue 
to run without emptying the Cavern, ’till the Feeding- 
Srream at O is fufficiently enlarged. So that by thefe 
different Conftru&ions of the Syphon, there may be 
fome Fountains which fhall flow conftantly in the 
Winter, or a wet Seafon, and intermit in the Summer, 
or a dry Seafon j and on the contrary, others which fhall 
flow continually in the Summer, or a dry Seafon, and 
intermit in the Winter, or a wet Seafon. There is a third 
Variety,which may arife from the Make of the Syphon, 
and will occafion fuch Irregularities as admit of no cer- 
tain Explanation. This happens when the Difcharge 
of the Syphon at the very laft is juft equal to the 
Feeding-Stream, and the Cavity of the Syphon at N 
