313 



the altitude of the planet, the relative situation of the planet and 

 moon, with any other circumstances of twilight or haze that were 

 likely to cause any incorrectness in the observation. To obviate the 

 uncertainty that will always attend the results of such observations, 

 from different states of weather, difference of telescopes, and imper- 

 fection of vision in different observers, Mr. Goldingham recommends 

 not to draw any inference from comparison of corresponding immer- 

 sions alone, without attending to the difference of corresponding 

 emersions also, by which all sources of error will be in a great degree 

 corrected. 



Electro-Chemical Researches on the Decomposition of the Earths; 

 with Observations on the Metals obtained from the alkaline Earths, 

 and on the Amalgam procured from Ammonia. By Humphry Davy, 

 Esq. Sec.R.S. M.R.I.A. Read June 30, 1808. \_PhiL Trans. 

 1808,;;. 333.] 



In the last Bakerian lecture mention was made of an apparent 

 decomposition of barytes and strontites into oxygen and inflammable 

 matter. 



In the prosecution of the same course of experiments upon lime 

 and magnesia, similar results were obtained ; for when either of these 

 earths was slightly moistened with water, and thereby rendered a 

 conductor of electricity from a powerful voltaic battery, inflammable 

 matter was developed at the negative surface, and oxygen at the po- 

 sitive. And these phenomena were not dependent on the presence 

 of water ; for when the same earths were made conductors, by being 

 in a state of fusion with boracic acid, analogous appearances were 

 produced. 



On account of the high inflammability of these bodies, similar ex- 

 periments were conducted under naphtha, with the hope of preserving 

 the products for examination ; but although dark opake specks, having 

 in some cases an appearance of metallic splendour, were produced, 

 yet, when heat was applied to them under boiling naphtha, there 

 was no appearance of fusion, and consequently no separation from 

 the surrounding undecompounded earth ; but when the mass was 

 afterwards thrown into water, an effervescence occurred, and evident 

 decomposition of the water. 



A series of experiments were next undertaken upon mixtures of 

 barytes or strontites, of lime or magnesia, of alumine or silex, with 

 potash ; and in the case of barytes and strontites, the potassium 

 formed was evidently not pure, but apparently alloyed by another 

 metallic substance. 



When barytes, strontites, or lime, was mixed with oxide of silver 

 or mercury, the compounds afforded analogous results when acted on 

 by the voltaic battery. 



When these experiments were resumed, after an interval of several 

 weeks, a battery had been prepared with 520 pair of plates ; and an 

 attempt was then made to unite the bases of these earths with the 



