1865.] Chemical Science. 739 



advantages to be that of not fouling the barrel, whilst the piece when 

 fired was subject to less recoil than in the case of gunpowder. 



Dr. David S. Price read an important communication, " On the 

 Action of Light upon Sulphide of Lead, and its bearing upon the 

 Preservation of Paintings in Picture Galleries." The author found 

 that the action of sulphuretted hydrogen upon lead-salts was greatly 

 influenced by exposure to the sun's rays, and that recently-formed 

 black sulphide of lead became bleached by conversion into sulphate 

 whenever the light had access. Hence it was not always desirable 

 to screen the face of oil paintings from the sunshine, but on the 

 contrary, an old practice seemed to confirm the author's scientific 

 conclusions, and he would recommend the occasional restoration of 

 such works of art by freely exposing to the light any pictures which 

 may be showing the effects of a tainted atmosphere. 



A very interesting discussion followed the reading of Dr. T. 

 Wood's paper, " On the New Formula?, with reference to Schools and 

 Examinations," the result of which lent authority for the general use 

 of the new system as being at once more truthful and better adapted 

 to the wants of the pupil than the old chemical notation. The 

 President and Professor Williamson spoke strongly in favour of its 

 general adoption, and urged the necessity of requiring its employ- 

 ment in all public examinations. 



The crystalline forms of Melaconite and Tenorite were defined by 

 Professor Maskelyne, and a most interesting account of certain 

 minerals from Norway and other localities was furnished by Dr. 

 David Forbes, who exhibited a collection of beautiful specimens 

 in the Museum of the Midland Instihite. " The Sanitary and 

 Economical Aspects of the Sewage Question," and " The Utilization 

 of Sewage, as conducted at Stroud," were treated of respectively by 

 Dr. A. Hill (Borough Analyst), and by Dr. H. Bird, of Cheltenham, 

 who coincided in advocating a return to a more primitive system of 

 house drainage, an opinion which received the support of Sir John 

 Bo wring. 



Messrs. Ladd and Oertling pointed out some important errors in 

 the indications of the Sikes's Hydrometer, which seem to demand the 

 attention of Her Majesty's Board of Inland Bevenue. A new vacuum 

 apparatus and Thermo-electric Pile were exhibited by Mr. William 

 Ladd ; a water barometer by Mr. Alfred Bird ; and a variety of 

 optical instruments by Mr. John Browning and Messrs. Powell and 

 Leland, of London, and by Messrs. Field and Co., of Birmingham. 



An interesting series of Photographs of the Interior of the Great 

 Pyramid, taken by the aid of the Magnesium Light, were forwarded 

 for exhibition by Professor C. Piazzi Smyth, together with a short 

 statement of the difficulties encountered in their production, which, in 

 the form of explanatory notes, was read by Mr. W. White. The 

 collection of photographs included several views of the granite coffer 

 in the King's Chamber, taken with measuring rods attached, and the 

 author asserts that the real dimensions closely accord with those 



