Meteorology.— Chemistry. 369 



13. Great Rain at Manchester in 1824. — According to the accurate obser- 

 vations of M. Dalton, the following extraordinary quantities of rain fell 

 during the four last months of the year : — 



September, - . 5.440 inches. 



October, - - r,.S9tt 



November, - 5.510 



December, - . 7.835 



Total, - 25.681 



The mean annual quantity of rain at Manchester is only about 34 in- 

 ches. 



14. Diurnal Variation of the Barometer at Marseilles. — M. Gambart, 

 the astronomer at Marseilles, has announced, that, in the year 1823, the 

 diurnal variations of the barometer have been the same as in the Torrid zone. 



chemistry; 



15. Deoxidating property of the Vapour of Water. — Professor PfafF, of 

 Kiel, has observed that nitrate of silver assumes a yellow or even a deep 

 brown colour, by exposure to the vapour of pure water; but the change 

 of colour does not appear till the solution is raised by the vapour to the 

 boiling point. M. PfafF attributes these changes of colour to deoxidation, 

 for the following reasons: 1. The similarity of the changes to those pro- 

 duced by light. 2. The disappearance cf the colour by the addition of 

 nitric acid. 3. The production of the same effect by the vapour of water 

 upon other metallic solutions, which are easily deoxidated by light or by 

 any chemical action., 4. The disengagement of oxygen gas during the 

 process. The most convincing proof, however, according to M- PfafF, is 

 furnished by a solution of gold, so diluted as scarcely to retain a yellow 

 tint. The vapour of water causes it to assume a fine blue colour, perfect- 

 ly similar to that produced by a tincture of galls. The acetate of silver is 

 much more feebly discoloured thon the nitrate. M. Gay-Lussac remarks 

 upon these results, that they do not leave a complete degree of conviction. 

 He says, that it is not necessary to make the vapour of water pass over the 

 solutions, but that their ebullition is sufficient. Ann. de Chim. tom.xxviii. 

 p. 21.5. 



16. Quantity of Heat disengaged during. Combustion. — In his remarks 

 on respiration, M. Dcspretz has found, that hydrogen gas in burning melts 

 315.2 times its weight of ice, and carbon 104.2. It is remarkable, as M. 

 Welter observes, that the number 315.2, and 104.2, are almost rigorously 

 proportional to the weight of oxygen absorbed by the hydrogen and the 

 carbon. For; from the chemical proportions of Berzelius, supposing the 

 first number 315.2, the second will be 104.0G6. This observation is favour- 

 able to the conjecture of M. Welter, that the quantities <>fhcal disengaged 

 in combustion, are in definite proportions — See the Ann- de Chim. tom. 

 VOL. II. NO. II. APRIL 1825. B b 



