Mons. C. Despretz on the Maximum Density of Liquids. 7 



point, and from the maximum to —13° Cent. The dilatation 

 is a little stronger below than above the maximum. 



This dilatation amounts to yjf ^ from 4° to 100°. 



Various points of the scale have been verified by fixed tem- 

 peratures, as that of aether, alcohol, &c. The curve of dila- 

 tation is almost a parabola for a very considerable space on 

 the scale. 



Extract from the Second Memoir, 



The question respecting the maximum of density of saline 

 solutions, immediately connected with the researches relative 

 to the temperature of the sea at various depths, has been for 

 a long time agitated among natural philosophers, who, how- 

 ever, are far from agreeing with each other on this subject ; 

 thus, as Ermann remarks, while Rumford, Marcet, and Ber- 

 zelius think that salt water has no maximum, Gay-Lussac, 

 Scoresby, and Sabine, guided by analogy, profess quite a con- 

 trary opinion*. 



The importance of the question had induced several phy- 

 sicists to attempt its solution by direct experiments, the only 

 way of bringing out the truth in such cases. 



Marcet (in 1819) read before the Royal Society of London 

 a memoir, in which he related some experiments by means of 

 which he had proved that sea-water contracts down to the 

 freezing point. He only says that the fluid ajjpeared to ex- 

 pand below 5°'Q Cent. 



Ermann, the son of the learned Secretary to the Academy 

 of Berlin, undertook in 1817, at the suggestion of Humboldt, 

 some observations for the same purpose. Four different me- 

 thods proved to this able physicist that there did not exist a 

 maximum for sea-water between 8° and — 3°. Science was al- 

 ready in possession of a memoir by Blagden, in which that 

 learned Englishman contended that the maximum sunk like 

 the freezing point, remaining at a distance equal to that of 

 pure water. It is impossible to account for the manner in 

 which Blagden was led to this conclusion, which is in oppo- 

 sition to all experiments made on this subject, none of which 

 gave to sea-water a maximum above the freezing point. 



Of the four methods described in my paper on the maxi- 

 mum of pure water, says M. Despretz, one only is appli- 

 cable to aqueous solutions. It is that in which the course 

 of a water thermometer is compared with that of a mercury 

 thermometer. In the experiments with saline solutions, as 

 in those with pure water, four thermometers filled with saline 

 solutions and four with mercury were immersed in a large 

 vessel, the temperature of which was gradually lowered to six 



• Captain Sabine's remarks on this subject will be found in Phil. Mag. 

 First Series, vol. |xiii. p. 70. — Edit. 



