58 



in a subliming chamber, where carbonate of ammonia from gas h'quor 

 was condensed; apparently in consequence of a local whirl affecting the 

 condensing pai'ticles. They were formed of acicular crystals, confusedly 

 grouped, without a trace of radiation or of any regular arrangement. 



4. On the Compressibility of Water. By W. J. Macquorn 

 Rankine, Esq., C.E. 



The results of the experiments of M, Grassi on the above subject 

 (Comptes Rendus XIX.) follow sensibly this law. 



The compressibility of water is inversely proportional to the 

 density, multiplied by the temperature as measured from the ab- 

 solute zero of a perfect-gas thermometer, viz. : — a point 274°'6 

 below the ordinary zero of the centigrade scale, and 462°'28 below 

 that of Fahrenheit's scale. 



Hence the compressibility of water follows sensibl_y the same law 

 with that of a gas. 



Let & be the compressibility of water per atmosphere ; D its 

 density, the maximum density being unity ; r the absolute tempera- 

 ture, then 



^ = kTd 



where 



K = 72 atmospheres per centigrade degree, or 

 40 atmospheres per degree of Fahrenheit. 

 D may be computed by the author's formula for the expansion of 

 liquids. — {Edinburgh New Philosophical Journal, October 1849.) 



Dr Gregory read a letter from his Grace the Duke of Argyll, 

 describing the locality of a white muddy deposit sent with the letter, 

 and exhibited in a dry state to the Society. The deposit occurs in 

 what appears to be an old channel between Loch Baa, at the foot of 

 Ben More in Mull, and the sea, passing through a dead flat. The 

 lake discharges itself now by another channel. Dr Gregory found 

 the deposit to be silicious, with a trace of organic matter, and to 

 consist entirely of the silicious cuirasses of infusoria, like the berg- 

 mehl of Sweden. Navicula viridis, and some bacillaria had been 

 observed in it by Dr Gregory, and Dr Douglas Maclagan, who under- 

 took a microscopical examination, found, besides Navicula viridis, 



