Page:Proceedings of the Royal Society of London Vol 1.djvu/267

Rh the brightness remaining on the north polar regions is not uniform, but is tinged with large dusky spaces, of a cloudy atmospheric, ap— pearance. From which, and the fore-mentioned changes of colour at the polar regions, added to the changes he has formerly observed in the belts, We have, he thinks, sufﬁcient reason to infer the exist- ence of a Satumian atmosphere.

The chemical effects produced by electricity have, Mr. Davy says, long been objects of attention; but the novelty of the phenomena, their want of analogy to known facts, and the apparent discordance of some of the results, involved the inquiry in obscurity.

It was very early observed, that acid and alkaline matter appeared in water acted upon by a current of electricity; but Mr. Davy soon found that the muriatic acid came from the animal or vegetable mat- ters employed to connect the two portions of water; for when the same cotton was repeatedly used, it ceased to be evolved. The soda, in like manner, was found to proceed from the corrosion of the glass tube, as it did not appear in water electriﬁed in an agate cup.

To be more certain of this effect, some distilled water was elec- triﬁed in two agate cups, by the current from 150 four-inch plates, the communication between the cups being formed by moistened amianthus. In the ﬁrst experiment soda was produced in the nega- tive cup, but __the quantity was much less than when glass tubes were used; and on repeating the experiment, its quantity decreased, so that in the fourth experiment the presence of soda was scarcely per- ceptible. in the residual water. The water in the other tube was sour, and appeared to contain nitrous acid, with excess of nitrous gas: As similar effects were produced by electrifying water in small gold cones, Mr. Davy suspected that some minute portion of saline matter had been carried over during the distillation of the water; notwith- standing it did not affect nitrate of silver, or muriate of barytes. And on evaporating a quantity of it in a silver vessel by a heat not ex- ceeding 140° Fahrenheit, a small residuum was actually left, which appeared to he a mixture of nitrate of soda with nitrate of lead. A portion of this residuum being added to water electriﬁed in the usual manner, and which had attained the maximum of its effect upon tur- meric paper, considerably increased these eﬂ’ects.

Water slowly distilled, being electriﬁed either in gold cones or agate cups, did not evolve any ﬁxed alkaline matter, though it exhibited signs of ammonia; but in tubes of wax, both soda and potash were evolved, and the acid matter in the positive cup was a mixture of sulphuric and muriatic acids. In a tube of resin the alkali was principally potash. In cups of Carrara marble, primitive marble from Donega], argillaceous schist from Cornwall, serpentine from theLizard, and grauwacke from North Wales, soda. was uniformly evolved.