278 BULLETIN OF THE 



last of the Newton rings shown previous to bursting. The result 

 arrived at from both sets of exjieriments was that water instead 

 of having a cohesion of 53 grains to the square inch (as was 

 very commonly stated), has a cohesive force of several hundred 

 pounds to the inch ; or that the intermolecular cohesion of a 

 Mquid is fully equal to that of the substance in the solid state.* 



In 1846, he presented to the Philosophical Society an epitome 

 of his views on the molecular constitution of matter; giving the 

 reasons for accepting the atomic hypothesis of Newton. He 

 pointed out that the discovery and establishment of a general 

 scientific principle " is in almost all cases the result of deductions 

 from a rational antecedent hypothesis, the product of the imagi- 

 nation ; founded it is true on a clear analogy with modes of 

 physical action, the truth of which have been established by 

 previous investigation :" and he urged that the hope of further 

 advancement lies in the assumption " that the same laws of force 

 and motion which govern the phenomena of the action of matter 

 in masses, pertains to the minutest atoms of these masses." He 

 therefore felt " obliged to assume the existence of an setherial 

 medium formed of atoms which are endowed with precisely the 

 same properties as those we have assigned to common matter." 



" According to the foregoing rules we may assume with Newton, 

 the existence of one kind of matter diffused throughout all space, 

 and existing in four states, namely the setherial, the aeriform, the 

 liquid, and the solid. "f In referring to this postnlated fourfold 

 state of matter, Henry was accustomed to point out the remark- 

 able analogy between this conception, and that of the four ele- 

 ments of the ancients, — fire, air, water, and earth 



" In conclusion, it should be remembered that the legitimate 

 use of speculations of this kind, is not to furnish plausible expla- 



* Proceed. Am. Phil. Soc. April 5, and May 17, 1844, pp. 56, 57, and 84, 

 85. The original notes of these interesting experiments containing the 

 numerical results obtained under a great variety of comlitions, laid aside 

 for further redactions and comparisons, were destroyed by fire in 1865. 

 Since the density of most solid substances differs very slightly from that 

 of tlieir liquid state, being indeed less in many, — unless at considerably 

 lower temperatures, (as in tlie case of ice, and most of the metals.) it 

 appears quite improbable that the difference between solidity and liquidity 

 could depend in any case on the degree of cohesion. On the contrary, 

 the cohesion of water sliould be sensibly greater than that of ice, since its 

 constituent molecules are closer together. Of the nature of that "lateral 

 adhesion'^ which resists the flow of solids (excepting under the conditions 

 of great strain — long continued), and whose absence is mark d in liquids 

 by their almost perfect and frictionless mobility, our present science affords 

 us no intimation. 



f Two hundred years ago, Newton speculating on the unity of matter, 

 ventured the suggestion, " Thus perhaps may all things be originated 

 from ffither." — Letter to the Secretary of the Royal Society — Henry Olden- 

 burg, January, 1676 {Hist, oj Roy. Soc. by Thomas Birch, vol. iii. p. 2o0). 



52 



