78 SaiBNTIFlC NEWS* 



made of glass, and coated with gum lac. Though infer/of 

 in sensibility to Coulomb's apparatus, it appears sufficiently 

 sensible for experiments of this kind, since eacli degree of de- 

 viation of the tongue of the balance from was equal to the 

 weight of 0-04 of a grain. The result of Mr. Simon's ex- 

 periments, the circumstances of which he varied in every 

 possible way, was, that the electric repnlf^ion was in the sim- 

 ple inverse ratio of the distance. In trials with the gold leaf 

 electrometer this law was established with still more precision 

 than in those which he made with the pith balls. It is 

 to be observed, that Volta has always denied the truth of 

 Coulomb's law, and asserted,that experiments with the elec- 

 trophorus show the electric repulsion and attraction to be 

 dimply in the inverse ratio of the distance. 

 Greatest den- Mr. Tralles has found by a very simple experiment, that 

 sitj of water, the temperature at which water possesses the greatest den- 

 sity is at 39*83° F., or 4*35 of the centesimal thermometer; 

 and he conceives this point, being more fixed than that of 

 congelation, should be taken as the 0, 

 Standard of Considering pure water at this density too as the proper 



*9s -'*''* unit for specific gravities, Mr. Trallas has given proper for- 

 mulae and a table for calculating specific gravities from this 

 unit according to the different heights of the barometer and 

 thermometer. Mr. Karsten has adopted these formulae in 

 calculating the specific gravities of minerals from his own 

 • experiments, with more accuracy than has usually been 

 done, for the new edition of his Mineralogical Tables just 

 published. 

 Answer to '" another paper in Gilbert's Annates der Physick, enti- 



Daiton. tied " Principles of Areometry, exhibited in the most gene- 



ral manner, and applied to the Vapour of Water, as a Cri- 

 tique on the Hypothesis of Dalton, and on some Calcula- 

 tions of theDensity of theVapour of Water," iVirTralles demon- 

 strates the insufficiency and erroneousness of Mr. Dalton's 

 hypothesis of the mode in which elastic fluids mix with each 

 other, and the constitution of the atmosphere. From the expe- 

 Specific gra- rimeuts he quotes the specific gravity of the vapour of water 

 ifUj of T4i)our. is to that of dry air as 1 to 1'45, in equal circumstances. 

 From the results of the experiments of Biot and Arrago 

 coiupured with those of Gilpin, he finds the density of dry 



