174 Proceedings of the Royal Physical Society. 



dicular depth, and not influenced by the size, or shape, or 

 position of the containing vessel." These two laws are 

 practically exhibited in the Accumulator in the following 

 fashion :— A reservoir of water is placed at a convenient 

 height from the power on which it is proposed to operate. 

 A heavy weight is made to press upon the reservoir, and a 

 communication is made with the engine which is to apply 

 the power gained, by means of a tube of very small dia- 

 meter. It is found that the power thus practically gained 

 is equal not to that represented by the pressure of the weight 

 upon the reservoir, but to that pressure plus the pressure of 

 an imaginary reservoir equal in depth to that of the connect- 

 ing tube from the reservoir to the engine.. 



If, then, natural reservoirs of water in the rocks have a 

 mass of superincumbent strata pressing on them, and a com- 

 munication be opened downwards by a narrow outlet, the 

 pressure at the spot where the outlet terminates must be 

 governed by the same laws. That such forces actually exist 

 is undoubted. And they may be a possible cause of such 

 natural phenomena as the reappearance of rivers which have 

 flowed for some time in a subterranean channel, the outburst 

 of fresh-water springs in the sea, or in places where no de- 

 clivity is known sufficient to account for their outburst on a 

 plain. 



When, however, we estimate the water which is absorbed 

 by porous strata as existing in a natural reservoir, and 

 pressed down by impervious strata above, this hydraulic 

 problem will have a much wider geological application. It 

 will likewise require nice discrimination to determine how 

 much the faults and fissures of the strata are due to this 

 cause, and in what degree to other physical forces. 



The amount of rain-fall is quite sufficient to afford the 

 means of such a power in almost any situation. It has been 

 calculated that every inch in the depth of rain falling upon 

 a single acre is equal to one hundred tons, so that there falls 

 3000 tons-weight of rain annually upon every acre, or, daily, 

 ffg tons. The rain-fall varies at certain seasons of the 

 year. Mr Bailey Denton states that, at Hinxworth, the 

 discharge from the open lands amounted, in January and 



