CATARACTS, AND INUNDATIONS. Q5 



receive the reader's approbation, he will be disposed to think, that 

 Pliny discovered the true nature of reciprocating fountains, when he 

 compared the fluctuations of these springs to the interrupted and 

 irregular stream which issues from a bottle. In fact, only one cir- 

 cumstance seems wanting to render his explanation of the pheno- 

 menon complete ; he has not informed his fiiend Licinius, how he 

 supposes the air gets into the subterranean channel, which supplies 

 his well with water. Perhaps ihi.s 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 re- 

 spiration 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 teli this ingenious and learned man, that he imagined 

 the outlet of the fountain had a communication under ground, witli 

 one of these spiracles of the globe. Be this as it may, the notion is 

 too absurd to be mentioned in the present improved state of Natural 

 Philosophy, in any other light than as a curious document of the 

 puerile conceits with which the philosophers of ancient times 

 amused thtir hearers. In the foregoing attempt to complete the 

 theory, 1 have had recourse to a well known phenomenon; water 

 is beaten into foam by being agitated; which was the case by Mr. 

 Swainston's vessel, because a strong current fell into it from the 

 pump. There is, however, one objection still remaining, which de- 

 serves to be considered: the levity of foam, compared with the 

 superior weight of water, may lead some persons to suspect, that 

 this light substance will not mix with water, but will float on the 

 surface of the reservoir, in which it is formed. Supposing this 

 suspicion to be well-founded for the sake of argument, we must 

 allow the foregoing theory of reciprocating vessels to be defective 

 in a very essential point : because if foam cannot sink, the air that 

 proceeds from it, cannot find its way into the tubes or siphons, 

 which convey the water from such vessels. Being unwilling to 

 leave this objection unanswered, I resolved to put the truth of this 

 principle to the test of direct experiment ; which was done in the 

 following simple manner: A small bell glass, being fir-t filled witii 

 water, was inverted in six quarts of the same fii.'H, contained in a 

 small tub. Things being thus prepared, the coatets of the open 



