SCIENTIFIC NEWS. 371 



magnetic forces increases with the latitude, as Mr. von Hum- The magnetic 

 boldt had already remarked on his American tour; for at ^^[^ c {^. & 

 Berlin it is 13703, while at Rome it is only 12642. It fol- tude. 

 lows too from their labours, that the influence of the chain ^^Alps lft- 

 of the Alps was very feeble, if any thing. That of Vesu- tie or nothing, 

 vius at the moment of the earthquake and eruption of 1805 ™f d °f in ^" 

 was not much more perceptible, and this would appear to eruption th« 

 be owing rather to local circumstances, than to a particular same ' 

 magnetic centre. 



The description of the instruments employed in these ob- 

 servations, and the disquisitions entered into by Mr. Gay-, 

 Lussac respecting the best means of making them, cannot 

 fail to add to the confidence, which the well-known accu- 

 racy and skill of the observers must naturally inspire. 



From eudiometiical experiments, and the analysis of the All gases sup- 

 air, Messrs. von Humboldt and Gay-Lussac had been led £^ tohl^" 

 to suspect, that all gases might have the same capacity for the same capa- 

 caloric. This consequence, which appeared deducible frota " lty * or heat i 

 their observations, deserved a more scrupulous examination, 

 which Mr. Gay-Lussac undertook on his return. His new 

 experiments confirmed those before made, yet led him to an 

 opposite conclusion. The gases he had observed with Mr. but this h true 

 von Humboldt had in reality nearly equal capacities for heat, °p e c t ^ som a. 

 but it was wrong to ascribe the same property to all gases 

 without distinction. 



The apparatus contrived by Mr. Gay-Lussac was ex- Gay-Lussac's 

 tremely simple. It consists of two equal globes, each with deteV^'nine 1 

 two tubulures, one fitted with a cock, the other with a very this. 

 sensible spirit thermometer. The globes having been freed 

 from moisture by dried muriate of lime, they were exhaust- 

 ed of air, and one was filled with the gas to be tried. The 

 communication between the two balloons being then opened, 

 part of the gas included in the first rushed into the second, 

 till an equilibrium was established; and then Mr. Gay- 

 Lussac carefully examined the changes of temperature indi- 

 cated by the two thermometers. 



In the first experiment, the subject of which was atmos- Air rushing m- 

 pheric air, he saw with astonishment the thermometer rising f ° ^"utbe t 

 perceptibly in the exhausted globe in proportion as the air 

 rushed into it. This fact appears diametrically opposite to 



another 



