and Spouting- Fountains. 233 



miles from the nearest point of the neighbouring coast of the 

 Junderbunds. Here, then, is a manifest instance of a subter- 

 ranean channel of water of more than a hundred miles extent. 

 And so soon as an incontestable fact extends to such a number 

 of miles as this, all the objections, such as we have just men- 

 tioned, that are based on the consideration of distance, imme- 

 diately, of course, fall to the ground. 



On the effects produced by Tides on some of these Fountains. 



M. Baillet has observed that the elevation of the projecting 

 fountain of NoyeUe-sur-Mer, in the Departement de la Somme, 

 rises and falls with the tide. I beHeve that it is the same with 

 all the similar fountains which have been sunk in the neigh- 

 bourhood of Abbeville. 



Where no means are aiforded us of appreciating the changes 

 which take place in the level, then we may determine, in a man- 

 ner not less satisfactory, the influence of the flowing and ebbing 

 of the tide, by measuring, at convenient epochs, the quantity of 

 water which issues from the fountains. 



Thus at Fulham, not far distant from the Thames, in the 

 property of the Bishop of London, there is an artesian well, 

 about 300 feet deep, which supplies now eighty and now sixty 

 gallons per minute, according as the tide is high or low. 



Let us inquire if this effect of the tides is as difficult of ex- 

 planation as, at first view, it would appear to be. 



If, on the sides of a vessel, of any shape, filled with water, 

 we drill a hole, the dimensions of which, when compared to the 

 size of the vessel, is very insignificant, the dribbling which will 

 take place through this opening, will not affect sensibly the state 

 of the original pressures. And so with two, three, or ten such 

 openings, so long as the whole of them put together are still 

 small — they will leave undisturbed the pressure which takes 

 place on every part of the vase which is somewhat removed 

 from these openings ; they will leave it such as it was, in a state 

 of equilibrium, as when the liquid was without any motion. But 

 on the other hand, if we were to make the opening, or the 

 openings, somewhat larger, all this would be immediately changed; 

 and the sizes which we gave the holes would influence the pres- 

 sure on every point ; so that if one of the openings was lessened, 



