1870.] Physics. 567 



vapour of water of a known tension and temperature. Under these 

 conditions results are obtained which prove that the decomposition 

 of vapour of water by iron while red-hot is rigorously subject to all 

 the laws which govern the tension of saturated vapours. 



M. E. Cappel has published a lengthy paper on the influence of 

 the temperature on the sensitiveness and delicacy of spectrum 

 reactions. The main result is, that the temperature most suitable 

 for the spectrum analysis of the alkalies is that of the oxyhydrogen 

 flame, and for the rest of the metals the heat of the electric spark. 

 The higher the temperature the more distinct the reactions. 



In some observations on the bats wing-burner flame, Dr. A. 

 Baudrimont states that the flame consists of two distinct portions, 

 one of which (the interior) has a comparatively low temperature 

 while it is surrounded by a luminous envelope, the temperature of 

 which exceeds that of molten platinum. Indeed the author found 

 that a platinum wire ^th mm. thick, when properly placed in this 

 flame, fused immediately. 



General Morin has experimented at the Conservatoire des Arts 

 et Metiers on some fire-clay stoves ; the results are said to be 

 highly satisfactory. The useful effect of heat given off by the fuel 

 amounts to 93 per cent. The air in the rooms where these stoves 

 were placed was not at all vitiated so as to incommode those pre- 

 sent, notwithstanding the interior of the stoves became thoroughly 

 red-hot. The author says that, taking all in all, these stoves, 

 when suitably connected with flues, will afford a cheap and in 

 every respect wholesome mode of heating apartments. 



A new material for the manufacture of crucibles is described by 

 M. J. Desnoyers. The substance known as gaize, or jpierre morte, 

 is a mineral largely met with in the departments of the Ardennes, 

 where it forms a deposit of some 100 metres thickness. Its specific 

 gravity is 1 '48. It is on being dug up quite soft, so that it can be 

 cut with a knife, but becomes hard on drying and very hard when 

 exposed to red-heat, whereby its specific gravity is reduced to 1 * 44. 

 This material is essentially a substance capable of withstanding high 

 temperatures; and the author exhibits crucibles made from the 

 gaize which have been used successfully for melting iron. Dr. La 

 Salvelat, the celebrated chemist of the Imperial Porcelain Works 

 at Sevres, states that layers of similar material exist in the central 

 parts of France, and that these minerals are of great value for the 

 construction of blast and other furnaces. 



By the term " rochage," H. Caron understands a peculiar pro- 

 duction of sparks, best seen when molten cast-iron is run off from 

 the blast furnace into moulds. In a lengthy paper the author 

 describes a series of experiments undertaken with the view to prove 

 that since steel and cast-iron, when molten in an atmosphere of 



