RECIPROCATING SPRINGS# 
189 
process here described, discovers the nature of the pheno- 
mena which are exhibited by Mr. Swainston’s vessel ; for the 
air, which separates from the water in the siphon, is col- 
lected in some part of that tube, most probably in a bend con- 
necting two adjacent legs; where it forms a bubble or mass, 
large enough to produce a considerable obstruction in the 
current, by contracting the area of the pipe. The water 
will evidently rise in the tub, so long as its efflux is inter- 
rupted by this obstruction ; but the action of the stream in 
the siphon will push the mass of air from place to place in its 
own direction until it shall be discharged at the nozle. The 
removal of this impediment will restore the stream to its full 
vigour ; upon which the water will begin to subside in the 
tub ; and it will continue to do so, until the surface arrives? 
at its proper level j unless a second collection of air happens 
to be formed in the mean time. We have now investigated 
the nature of the reciprocation, observable in Mr. Swainton’s 
apparatus, it proceeds entirely from the obstruction of ait* 
bubbles, lodged in the crooked canal ; the formation of 
which depends on causes that act in a fortuitous or irregular 
manner 5 consequently the reciprocation which results from 
their united operations will prove to be equally uncertain and 
variable. 
Should the preceding theory of an ebbing and flowing vessel pjj n y disco- 
receive the reader’s approbation, he will be disposed to think, vered this 
that Pliny discovered the true nature of reciprocating fountains, comparing the 
when he compared the fluctuations of these springs to the in- effects to the 
terrupted and irregular stream which issues from a bottle. In bou/e -ImUie 
fact, only one circumstance seems wanting to render his ex- did not ac- 
planation of the phenomenon complete; he has not informed ^? untfor 
his friend Licinius, how he suppdses the air gets into the sub- 
terranean channel, which supplies his well with water. Per- 
I haps this omission was the effect of design, rather than of 
negligence; for many philosophers in Pliny’s time held the 
singular opinion, that the earth possesses the faculty of respi- 
ration like animals ; in consequence of which it inhales and 
expires air through the crannies and caverns, which extend to 
its surface. Supposing Licinius to be of this way of thinking, 
Pliny had no reason to tell this ingenious and learned man, 
that he imagined the outlet of the fountain had a communi- 
cation 
