286 Chronicles of Science. [Ap r ^ 



spectrum of Neptune consists chiefly of three lines, or bands, placed 

 near the green, and that its light is entirely devoid of red ; this is 

 confirmed by the colour exhibited by the planet when seen through 

 a telescope, which is a sea-green. 



M. Feil has exhibited before the French Academy samples of 

 perfectly homogeneous heavy flint-glass for optical purposes free 

 from any bubbles or defects, and in masses weighing from 25 to 

 35 kilos. The process whereby this is obtained is not explained ; 

 but the statement is made that the crucibles having been protected 

 from the effects of the lead, a heavier glass even than Faraday's 

 can be made. The maker sent also a set of samples of beautifully- 

 made artificial precious stones, not mere specks, but of good size. 

 The aluminates of lime, of baryta and lime, of lead and of bismuth, 

 are proposed for flint-glass ; and the aluminates of magnesia and 

 the silicates of magnesia and alumina for crown-glass. 



M. Bontemps, the managing director of the celebrated glass 

 works at Choisy-le-Eoi, has arrived at the following results in con- 

 nection with the coloration of glass under the influence of direct 

 sunlight : — Within three months after having been exposed to sun- 

 light, the best and whitest glass made at St. (xobain is turned very 

 distinctly yellow ; extra white glass (of -a peculiar mode of manu- 

 facture) has become even more yellow, and gradually assumes a 

 colour known as pelure cVoignon ; glass containing 5 per cent, of 

 litharge was also affected, but far less perceptibly; crystal glass, 

 made with carbonate of potassa (the other varieties referred to 

 contain carbonate of soda), litharge and silica, was not at all affected ; 

 English plate-glass, made by the British Plate- Glass Company, 

 and exhibiting a distinctly azure-blue tinge, remained also un- 

 affected. The author attributes the coloration, which begins with 

 yellow and gradually turns to violet, passing through red jpelure 

 oVoignon, to the oxidizing effects of the sun's rays upon the pro- 

 toxides of iron and manganese contained in glass. 



M. Schinz states that platinum brought to bright white heat 

 by means of the ignition of a mixture of hydrogen and carbonic 

 oxide gases, yields a light which, in relation to good coal-gas, is as 

 1-24 to 1-0. 



Professor B. Silliman has examined, in a lengthy series of ex- 

 periments, the relation between the intensity of light produced from 

 the combustion of illuminating gas and the volume of gas consumed. 

 His experiments prove, among other matters, this theorem — that 

 the intensity of gas-flames (i. e. illuminating power) increases, 

 within the ordinary limits of consumption, as the square of the 

 volume of the gas consumed. The chief point of interest, for the 

 consumer of gas, to be deduced from the data here presented is, that 

 where it is important to obtain a maximum of economical effect 



