Observations, &c. 355 
culties, which are not easily surmounted. It 
is not necessary to seek for examples to cor- 
roborate the preceding assertion; for, in all 
probability, most philosophers will be able to 
establish the truth of it, by incidents which 
are preserved in the private histories of their 
own speculations. In my opinion, however, 
_ the writers on Hydraulics furnish a striking 
instance of the fact inthe machinery, which 
they commonly employ for the’ purpose of 
explaining ‘the causes of reciprocating foun- 
tains, or of ebbing and flowing wells as they 
are called in vulgar language. 
Springs of this description may be reckoned 
amongst the rare productions of nature; the 
infrequency of which leads me ‘to conclude, 
that but few thinking men have had an oppor- 
tunity of observing a number of them with 
attention, and of comparing their operations ; 
for it is certain, that by far the greatest part 
of the world knows nothing of the subject, 
except by report. This want of ocular infor- 
mation, in all probability, has obliged specu- 
lative writers to rest content with the few 
facts, which are to be found in books; and 
Iam only acquainted with the following nar- 
ratives, which can be said to throw any light 
on the curious properties of reciprocating 
fountains. The first that I shall mention, 
Yy2 
