HYDROSTATICS. 



23 



pointed, we were obliged to go and 

 take some little refreshment at our inn, 

 after which we intended to come back 

 and spend the rest of our time by the 

 fountain, before we returned home. They 

 told us in the house that many had 

 been disappointed in this manner, and 

 the common people superstitiously im- 

 puted it to I know not what influence 

 which the presence of some people had 

 over the fountain ; for which reason 

 they advised, that, in case it did not 

 flow and ebb when we were both pre- 

 se t, one of us should absent himself, 

 to try whether it would do so in the 

 presence of the other. Upon our re- 

 turn to it, the man, who was still at 

 work, told us that it had begun to flow 

 and ebb about half an hour after we 

 went away, and had done so ten or 

 twelve times in less than a minute. 

 We saw the stream coming into the 

 basin, and likewise the others on the 

 outside of the basin begin to increase, 

 and to flow with great violence, upon 

 which the surface of the water in the 

 basin rose an inch and a quarter per- 

 pendicularly, in near the space of two 

 minutes ; immediately after which, the 

 stream began to abate again to its ordi- 

 nary course, and in near two minutes 

 time the surface was sunk down to its 

 usual height, where it remained two 

 minutes more ; then it began to flow 

 again as before, and in the space of 

 twenty-six minutes, flowed and ebbed 

 five times ; so that an increase, de- 

 crease, and pause, taken together, were 

 made in about five minutes, or a little 

 more. I could observe, by the mark 



upon the stones, that the surface o 

 the water in the basin had rose before 

 we came, at least three-quarters of an 

 inch perpendicularly higher than we 

 saw it ; and I thought that I could per- 

 ceive some very little abatement each 

 turn, both in the height, and in the 

 time of its sinking ; but the time of the 

 pause, or standing on the surface at its 

 usual height, or equable running of 

 the stream, was lengthened, yet so as 

 to leave some abatement in the time of 

 the rising, sinking and pause taken 

 together." (Phil. Trans. No. 424.) 



It should seem that, in the hill from 

 which this stream comes, there are 

 three hollows, or reservoirs, of different 

 sizes, and connected by syphons of 

 different widths. The times" of the in- 

 crease and decrease lengthening, arises 

 from the water sinking in one of the 

 reservoirs, which makes it flow more 

 slowly than when it is full. 



In some places there are springs 

 which run freely in summer, on in dry 

 weather, and almost stop in winter, or 

 in wet weather. This is owing to a 

 hollow in the hill being fed by runners, 

 but having beside the vent through 

 which the spring flows out, a waste, 

 pipe, formed higher up, like .a syphon, 

 which carries off all the water another 

 way as soon as the space is filled high 

 enough. Thus, while the water is low in 

 diy weather, this waste pipe does not 

 act, and the water flows out through the 

 spring ; but as soon as the rains make 

 the water rise high enough, the na- 

 tural syphon drains it off the other 

 way, and the only water that can run 



24. 



