Inquiries into the Principles of Liquid Attraction. 97 



that of a column of water seven feet j% of an inch in height, and 

 when the diameter is diminished to the j^g of an inch, the pressure 

 will be equal to that of a column of water twenty eight feet three 

 inches in height^ and so on in the same inverse ratio. 



Novvf it is known that the atmosphere may be compressed in pro- 

 portion to the weight or force to wliich it is subjected ; and if we 

 take a minute portion of air of the medium density, and subject it to 

 the pressure of a column of water of thirty two feet, its magnitude 

 will be diminished one half; and for every similar column which 

 may be added, the magnitude of the portion of air will be proportion- 

 ably diminished ; and if we add to the pressure which a minute por- 

 tion of air sustains from the contractile surface, the pressure which it 

 must sustain at the various depths in v/ater where we find it, it is easy 

 to conceive, in strict conformity to the results which have been pre- 

 sented, that it sustains the pressure of several atmospheres. 



If we may be allowed to reason from analogy, it will appear, by 

 comparing the magnitude of drops of water and of mercury, that the 

 contractile force of the surface of mercury exceeds that of the sur- 

 face of water, nearly in the ratio of their specific gravities. 



Lastly ; the attraction of different substances for the surfaces of 

 liquids, has a strong resemblance to chemical affinities ; where the 

 smallest particles have an attraction for each other, which attraction, 

 when compared with the force of their gravitation, exceeds all ex- 

 pression by numbers. 



Remarks. — In reviewing the above explanation of the laws of liquid 

 attraction, it appears necessary, in order to avoid misconception, to 

 observe, that the term capillary has been applied to tubes which are 

 not strictly so. By " capillary tubes," I understand those whose bores 

 are so exceedingly minute, that the water, or other liquid, which is 

 in them, may be said to have lost its peculiar character as a liquid, 

 and to have assumed active properties. The tubes which have been 

 considered are either artificial, as glass, or natural, as quills and 

 straws, and such as were not intended to contain circulating active 

 fluids, but to contain air. 



The two states of a liquid, viz. the contractile state of the particles 

 of the surface, and the passive state of the particles beneath the sur- 

 face, are both of them to be considered as the effects of attraction^ 

 modified by circumstances. 



By inspecting Fig. 1 , which represents a vessel whose sides make;, 

 internally with the bottom, acute angles, it will be seen how a greater 



Vol.. XVII.— No. 1. 13 



