Intelligence and Mtscellaficoiis Articles. 541 



Prof. Locke strongly urges the ])ropriety of multiplying observa- 

 tions upon these phsenomena, in order to develope the general law ; 

 and concludes by returning his thanks to Col. Sabine and the British 

 Association for the kindness and liberality with which they have ten- 

 dered their assistance in his labours. — Proceedings of the Amer. Pliil. 

 Soc, vol. iv., p. 63. 



COHESION OF LIQUIDS. 



Prof. Henry made a verbal communication to the American Philoso- 

 phical Society, on April 5th, 1844, relative to the cohesion of liquids ; 

 in which he stated that very erroneous ideas are given as to the con- 

 stitution of matter in the ordinary books on Natural Philosophy. The 

 passage of a body from a solid to a liquid state is generally attributed to 

 the neutralization of the attraction of cohesion by the repulsion of the 

 increased quantity of heat ; the liquid being supposed to retain a small 

 portion of its original attraction, which is shown by the force neces- 

 sary to separate a surface of water from water in the well-known ex- 

 periment of a plate suspended from a scale beam over a vessel of the 

 liquid. It is, however, more in accordance with all the phccnomena 

 of cohesion to suppose, instead of the attraction of the liquid being 

 neutralized by the heat, that the effect of this agent is merely to neu- 

 tralize the polarity of the molecules so as to give them perfect free- 

 dom of motion around every imaginable axis. The small amount of 

 cohesion (53 grains to the square inch) exhibited in the experiment 

 above alluded to, is due, according to the theory of capillarity of 

 Young and Poisson, to the tension of the exterior film of the surface 

 of water di'awn up by the elevation of the plate. This film gives 

 way first, and the strain is thrown on an inner film, which, in turn, 

 is ruptured ; and so on until the plate is entirely separated ; the 

 whole effect being similar to that of tearing the water apart atom by 

 atom. 



Reflecting on this subject. Prof. Henry had thought that a more 

 correct idea of the magnitude of the molecular attraction might be 

 obtained by studying the tenacity of a more viscid liquid than water. 

 For this purpose he had recourse to soap water, and attempted to 

 measure the tenacity of this liquid by means of weighing the quan- 

 tity of water which adhered to a bubble of this substance just before 

 it burst, and by determining the thickness of the film from an obser- 

 vation of the colour it exhibited in comparison with Newton's scale 

 of thin plates. Although experiments of this kind could only fur- 

 nish approximate results, yet they showed that the molecular attrac- 

 tion of water for water, instead of being only about 53 grains to the 

 square inch, is really several hundred pounds, and is probably equal 

 to that of the attraction of ice for ice. The effect of dissolving the 

 soap in the water is not, as might at first appear, to increase the 

 molecular attraction, but to diminish the mobility of the molecules, 

 and thus to render the liquid more viscid. 



Prof. Henry, in a second communication, (made on the 1 7th of 



