570 Astronomical Olservations at Hackney Wick. [Mat^ 



converted into sulphate, and no crystals appeared on cooling the 

 liquor. 



6*. Sulphate of lead, boiled in diluted muriatic acid, was 

 decomposed and dissolved j crystals of muriate of lead formed 

 ou cooling the solution. 



Sulphate of soda, therefore, does not decompose muriate of 

 lead when an excess of muriatic acid is present, and sulphate of 

 lead is decomposed by muriatic acid, and muriate of lead by 

 sulphuric acid, a case of affinities that cannot easily be explained. 



I have been thus particular in describing the properties of this 

 substance, from the circumstance of its being the only instance, 

 with which 1 am acquainted, of a salt composed of different 

 acids united to different bases; which peculiarity, if found to 

 extend to a greater number of bodies, may throw some addi- 

 tional light on our knowledge of affinity. 



Since the investigations of chemists have made known the 

 nature and properties of triple salts, some of the most obscure 

 parts of practical chemistry have been rendered comparatively 

 plain ; but there are yet several circumstances connected with 

 the salts that cannot satisfactorily be explained ; and until their 

 affinities are more accurately ascertained, by the discovery and 

 examination of a greater number of substances composed of 

 different genera of salts, we can have but a partial knowledge of 

 the influence which some of them have in preventing the crys- 

 tallization of others, and of the true reason why certain saline 

 bodies are more soluble in the solutions of others than in water 

 alone. 



Article VII, 



Astronomical Observations at Hackney Wick. By Col. Beaufoy. 



Latitude 5i° 32' 40" North. Longidide West in Tiaie 6'82" . 

 1813. 



Time tit H. W, 



Mar. 26, emersion of Jupiter's ist. satellite. . 10?! 43' 52" 

 April 11, Ditto Ditto 1st Ditto 9 

 April IS, Commencement of the egress of ^ g 



J«piter's4th satellite from his disc ) 



April IS, emersion of Jupiter's 2d satellite. .10 

 Jk-pril 17, immersion of y Librse ^ jq 



02 

 57 

 18 

 24 



05 

 33 

 05 

 28 



Time at 



IQh 43' 

 9 02 



GreenwicTi. 



58" 82'" 

 12 82 



59 82 



11 82 



(N. B. The Moon's Limb Avas very tremulous.) 



N. B. The Observations are in Mean Time. 

 Rain between March the Ist and 31st, 0'662 inches. 



