244 NATURAL THEOLOGY. 



Suppose a machine formed of two boards of 

 equal diameter, and joined together by leather 

 nailed to their margins like a pair of bellows : a 

 hole is made in the upper board into which is in- 

 serted a tube. Now, if a person mount upon this 

 apparatus when it is filled with water, and blow 

 into the tube, he can raise the upper board, car- 

 rying himself upwards by the force of his own 

 breath — indeed, by the power of his cheeks alone. 

 It is on the same principle that, when a forcing 

 pump is let into a closed reservoir of water, it 

 produces surprising effects. The piston of the 

 hydraulic press being loaded with a weight of one 

 pound, the same degree of pressure will be trans- 

 mitted to every part of the surface of the reservoir 

 that is given to the bottom of the tube, and the 

 power of raising the upper lid will be multiplied 

 in the proportion that its surface is larger than 

 the diameter of the tube. Or, to state it con- 

 versely: suppose we had to raise the column of 

 water in the tube by compressing the reservoir, it 

 would require the weight of a pound on every 

 portion of the superficies of the reservoir equal 

 in extent to the base of the piston, before the 

 w^ater could be raised in the tube. If the appa- 

 ratus which we have described were full of air 

 instead of water,we should witness a similar effect ; 

 for all fluids, w^iether elastic or not, press equally 

 in all directions ; and this is the law on which the 

 phenomenon depends. If we blow into the nozle 

 of a common pair of bellows, it is surprising what 



