1870.] Physics. 287 



from the consumption of a given volume of illuminating gas, this 

 result is best obtained by the use of burners of ample flow. 



Heat. — According to MM. Troost and Hautefeuille, carbon 

 when combining with oxygen, only gives out 8000 caloric units; 

 boron, under the same conditions, yields 14,400 caloric units ; while, 

 when boron combines with three equivalents of chlorine, 104,000 

 caloric units represent the heat set free. 



The heat disengaged by the combination of 1 grm. of amor- 

 phous silicium with oxygen is 7830 units, with chlorine 5030. 

 When 1 grm. of chloride of silicium reacts upon 140 times its 

 weight of water, it is 2915 ; the heat disengaged when 1 grm. of 

 amorphous silicium is converted into crystallized silicium is 290 

 units of heat. 



Dr. St. Claire-Deville states that the oxygen dissolved during 

 the fusion of platinum causes this metal to present the same pheno- 

 menon as molten silver — viz. scintillation and spirting while in the 

 molten state. 



In a paper " On the Heat given off by the Moon's Kays," 

 M. Zantedeschi states that, as far back as the years 1685 and 1781, 

 the Italian savants Geminiano, Montanari and Paolo Frisi proved 

 the existence of rays of heat emitted by the moon, by means of 

 lenses and ordinary thermometers. The author refers to his 

 observations made some twenty years ago, when he applied thermo- 

 electric apparatus, as well as spirit thermometers and lenses, and 

 obtained results fully confirming those made and recorded by the 

 Italian savants just alluded to. 



In Germany the doors of the steam-boiler furnaces are now very 

 generally provided with square pieces of mica, properly fastened, by 

 means of which the fireman is enabled to observe the fires without 

 the necessity of opening the furnace-doors too frequently, which is 

 injurious, on account of interfering with the draught and proper 

 course of combustion of the fuel, by reason of the access of irregular 

 currents of cold air. Mica withstands a very high temperature ; and 

 the accidental breakage of the squares of this substance is guarded 

 against by a properly-constructed iron- wire guard outside. 



Dr. Ziurek states that gas from the brown coal from Fursten- 

 wald, five miles from Berlin, will shortly be made on the spot, and 

 collected in Berlin in twelve gas-holders, each of a capacity of 

 750,000 cubic feet. The gas will be carried, as usual, in under- 

 ground mains, and chiefly applied for heating purposes. 3000 cubic 

 feet of this gas have a heating power of one-third of a ton of best 

 coals, and are equal to 1 ton of best Prussian brown coal. 1000 

 cubic feet of this gas will cost about 5d. in Berlin ; and the equi- 

 valent value of the heating power of this gas as compared with a 



