ON CAPILLARY TUBES AND SIPHONS. 



$. Those persons would be deceived who should imagine, that 

 tiie lightest liquors rise to the greatest height in these tubes : of 

 aqueous liquors, spirit of wine is that which rises to the least height. 

 In a tube in which water rises 26 lines, spirit of wine rises only 9 

 or 10. The elevation of spirit of wine, in general, is only the half 

 or a third of that of water. 



This elevation -depends also on the nature of the glass : in certain 

 lubes, water rises higher than in others, though their calibres be the 

 same. 



To be convinced that these effects are not produced by any thing 

 without the tube or the liquor, it is necessary to see these pheno- 

 mena, which are indeed the same in a vacuum, or in air highly rare- 

 fied, as in the air which we breathe. They vary also according to 

 the nature of the glass of which the tube is formed ; and they arc 

 different according to the nature of the fluid. The causes there- 

 fore must be sought for in something inherent in the nature of the 

 tube, and in that of the fluid. 



This cause is generally ascribed to the attraction mutually exer- 

 cised between glass and water. This explanation has been contro- 

 verted by Father Gerdil, a Barnabite and an able philosopher, who 

 has done every thing in his power to overturn it. On the other 

 hand, M. de la Lande has stood forth in its defence, and is one of 

 those modern writers who have placed this explanation in the, 

 clearest light. The reader may consult also, on this subject, a very 

 learned and profound memoir by M. Weitbrecht, in the Memoirs otj 

 the Imperial Academy of Sciences at Petersburg}!. 



When philosophers saw water rise in a capillary tube, above the 

 level of that in which it was immersed, or above that at which it 

 stood in a wider tube, with which it formed an inverted siphon, 

 they were induced to conjecture the possibility of a perpetual mo- 

 tion ; for if the water, said they, rises to the height of an inch 

 above that level, let us interrupt its ascent, by making the tube 

 only three quarters of an inch in height : the water will then rise 

 above the orifice, and falling down the sides into the vessel, the 

 same quantity will again rise, and so on in succession* Or, if the 

 water that rises in the capillary branch of a siphon be conveyed, by 

 an inclined tube, into the other branch, a continual circulatiou of 

 the fluid will take place ; and hence a perpetual motion given bv 

 nature. 



VOL. III. 2 E 



