454 M. G. Van tier Mensbrugge on the 



organic materials, vegetable or animal, gave much more 

 marked results: thus paper, first dried and then impregnated 

 with water, received a rise of temperature of 4°'52 ; sponge, 

 l°-9 : starch, 9°'7 ; iris-root, 6°'12 ; liquorice-root, 10 a 2 ; 

 ox-tendon, 3°*16 ; and the very thin membranes of the in- 

 testines of sheep, 9°*6 with water, and 10 o, 12 with alcohol. 

 These results, so surprising, compared with equation (1) ap- 

 pear to furnish, for the extreme tenuity of the ultimate organic 

 particles into which liquids can penetrate, a proof at least un- 

 expected, if not as certain as microscopic observations. 



Pouillet's experiments were followed up in 1855 by M. 

 Jungk *, who established the following facts : — (1) in water 

 absorbed by sand, there is depression or elevation of tempe- 

 rature, according as the initial temperature of the liquid is 

 below or above + 4°C; (2) the temperature is diminished 

 in water at 0° absorbed by snow. These two facts, intimately 

 connected with the abnormal expansion of water in the in- 

 terval between its maximum of density and its freezing-point, 

 appear to me again to spring immediately from equation (1). 

 If my explanation were true, we should have the theory of 

 regelation without the cooperation of external pressure. I 

 reserve the examination of this point, again, for a special 

 study. 



But, in my opinion, the accuracy of equation (1) is shown 

 especially by the excellent researches published in 1873 by M. 

 Melsens f, which so well complete the preceding investigations. 

 He has, in fact, found, as by an admirable intuition, the best 

 conditions of the phenomena of imbibition : not only has he 

 precisely estimated the quantities of material, solid or liquid, 

 employed, as well as the intervals of time elapsed from the 

 commencement of the absorption till the observation of each 

 of the successive temperatures, but he has also operated on 

 small quantities of solid material (charcoal) and slight quan- 

 tities of various liquids. Thus, with 10 grammes of charcoal 

 and 25 cubic centims. of liquid, the rise of temperature was 

 4° for alcohol, 6° for rectified ethylic ether, and 17° for sul- 

 phide of carbon ; lastly, 11 grammes of charcoal and 97 

 grammes of liquid bromine supplied to M. Melsens a heating 

 amounting to 30°, while only 4*45 grammes of charcoal and 

 33 grammes of bromine gave him, in a very short time, a rise 



* " Ueber Temperaturerniederung bei der Absorption des Wassers 

 durch feste porose Korper," Pogg. Ann. vol. exxv. p. 292. 



t " Notes chimiques et chiniico-physiques, 5 me Note, chap. 1 : De 

 l'elevation de temperature produite par l'imbibition du charbon par l'eau, 

 l'alcool, Tether ethylique, le sulfure de carbone et le brome/' Mem. de 

 V Acad, royale de Belgique, collection in-8vo, t. xxiii. 



