314? A DJJJertation on the 



upper furface ; Reafon demonflrates, that fuch a tube 

 cannot raife more water than it C2X\ fiijlain ; fince the 

 nearer the fluid is, the ftronger is the attractive force. 

 Experiment confirms this conclufion ; for a capillary 

 tube, however fhort, cannot be made to run over.— 

 The force of capillary attradion, alfo, will raife water 

 but to a very moderate height. The propofi.tion found 

 in mod Treatifes on Hydroflatics-r-T/?^^ the height to 

 which fluids rife in capillary tubes, is inverfely as the diam- 

 eter of their bores— h2iS led many to the erroneous con- 

 clufion, that if the bore is indefinitely fmall, the fluid 

 will afcend to an indefinite height. But the fa6l is 

 otherwife. Dr. Hooke, after many experiments with 

 what he calls cobweb tubes, was unable to raife water in. 

 them more than 21 inches. — Should we, therefore, 

 fuppofe fuch du6ls to exifl; in the earth of the requifite 

 length and pofition, capillary attra<5lion would not raife 

 water in any of them to a greater height than 21 inch- 

 es ; nor, even in thofe of a lefs length, would it caufe 

 the fluid to run over. 



Others allege, that if a fmall heap of aflies or fand 

 is put into a bafon of water, the water will rife through 

 it, above its own level, to the top of the heap. They 

 compare the Dry Land to the heap of aflies ; and the 

 Ocean to the warer of the bafon ; and infift that the 

 water of Springs rifes in the fame manner through hills 

 and mountains.- — I am not informed, that any experi- 

 ments have been tried to afcertain the height, to which 

 water will thus afcend through afhes, or through fand. 

 The caufe of its afcent, however, is well known to be 

 a mutual attracbion fubfiiling between the particles of 

 aflies or fand, and thofe of water. Whether this atr 

 traction be chemical or mechanical, it is to me felf evi- 

 dent, that no attradion can raife more water than it 

 Q2.i\ fuftain.— \i it is chemical, it will continue to raife 

 the fluid until the heap is thoroughly y^/wr^/fc/, and no 

 longer. Should the other particles of the fluid attempt 

 to fupplant thofe which were firfl; combined, thefe 

 would effecluaily refill the attempt by the right of &£■> 



