248 Intelligence and Miscellaneous Articles. 



obtained by these physicists, the author thinks that they do not 

 confirm their explanation, according to which the vibration com- 

 municated to the soldering of two heterogeneous bodies directly 

 produces an electric current. He thinks that the production of the 

 heat precedes that of the electric current. It is seen, on examina- 

 tion, how the existence of the current is connected with the vibration 

 — that the current ceases with the vibration, but not directly as if it 

 had been interrupted by cutting the wire. 



It appears natural to consider the electric effect observed in these 

 experiments as a resultant of the heat disengaged at the surface of 

 contact of two heterogeneous bodies which tend to enter into a 

 common vibratory motion. — Comptes Rendus, vol.1, pp. 656, 729; 

 BibliotKeque Universelle, vol. viii. p. 151. 



ON THE DENSITY OF ICE. BY M. L. DUFOUR. 



The question of the density of ice is certainly not settled. The data 

 of different authors vary considerably, and even the latest researches 

 have not led to very concordant results. In 1807, Placidus Hen- 

 rich found this density to be 0*905 ; subsequently it was found by 

 Thomson to be 0*94; Berzelius, 0*916; Dumas, 0950; Osann, 

 0*927 ; Pliicker and Geissler, 0*920 ; C. Brunner, 0*918 ; and lastly, 

 H. Kopp, in 1855, found that it was 0*909. These divergencies, 

 expressed in the increase of volume at the moment of congelation, 

 correspond to values between ± and -fa. 



In a series of researches on the congelation of water and of saline 

 solutions, the author has had occasion to investigate the density of 

 ice. The method which he has chosen, in order to avoid the serious 

 difficulties incident to the use of the ordinary methods in the case of 

 ice, consists in forming a liquid in which ice floats in equilibrium, 

 and then determining the density of this liquid. The liquid was a 

 mixture of water and alcohol, and all necessary precautions were 

 taken to avoid, as much as possible, sources of error. Preliminary 

 trials on bodies of known density showed that the method gave an 

 approximate value which was not more than 0*002 from the true. 

 The ice was quite free from air, and was obtained from distilled 

 water boiled for some time. The method gave a ready means of 

 determining the highest and lowest level of the density of each 

 specimen. 



The details of the research are published in the Bibliotheque Uni- 

 versellede Geneve for June 1860. For the majority of the specimens 

 examined, 0*922 or 0*923 was certainly the highest, and 0*914 the 

 lowest limit of the density. Twenty-two experiments gave a mean 

 density of 0*9175 with a mean deviation of ± 0*0007. The greatest 

 deviations were + 0*002 and —0*0013. 



The number 0*9175, which may be safely taken as giving the 

 density of ice at 0° C, is almost exactly that of C. Brunner 

 (0*9 180), which was obtained by a different method. This corre- 

 sponds to an increase of volume at the moment of congelation of 

 yj^, or very nearly T i r . — Comptes Rendus, June 4, 1860. 



