182 AXNCAL OF SCIENTIFIC DISCOVERT. 



Effect of Artificial Light on the Green Color of Plants. — M. Er- 

 mins, in the "Revue Horticole," records the following fact: Some 

 lilacs were placed for forcing in a heated cellar, partially lighted 

 with gas ; those leaves that were exposed to the light became 

 green, as if they had been in the open air, while the remainder 

 were etiolated. 



Light from Metallic Carbons. — M. Carre recently exhibited to 

 the French Academy some of his metallic carbons, or carbons im- 

 pregnated with iron, antimony, etc., which were found to give a 

 light over one-third more powerful than that obtained from the 

 ordinary carbon employed for the electric light. 



Annual Amount of the Sun'^s Heat on the Earth. — Pouillet has 

 made observations with a pyrheliometer, from which he estimates 

 that the amount of heat annually received by the earth from the sua 

 would melt a crust of ice surrounding the earth 101 feet thick. 



Liternal Stratum of Livariable Temperature. — The heat which 

 the earth receives from the sun does not penetrate more than 

 from 50 to 100 feet. At Paris this stratum of invariable tempera- 

 ture is found at a depth of 86 feet. 



Power of the Suns Rays. — A lens has recently been made for 

 IVfr. Parker, of London, 3 feet in diameter, 3 inches thick in the 

 centre, and weighing 212 pounds. In the focus of this powerful 

 lens the most refractory metals are almost instantly fused and 

 completely dissipated in vapor, while unyielding stony substances 

 are as readily vitrified. 



Fusion of Glass. — Herr C. Sching has shown, by the appli- 

 cation of the thermo-electric pyrometer, that the temperature of 

 a glass furnace in operation is only from 1,100*^ C. to 1,250^ C. 

 Crystal glass becomes completely liquid at 929° C, and is worked 

 at 833*^ C. A Bohemian glass tube softens at 769° C. and becomes 

 liquid at 1,052'^ C. Pure limestone loses its carbonic acid by heat- 

 ing for several hours at 617'^ C. to 675'' C. The gas can be driven 

 off more rapidly by increasing the temperature. 



New Pgrojneter. — A new pyrometer of English make, designed 

 by M. Wood, of the Tees Iron Works, consists of a metallic tube 

 connected at one of its extremities to a pillar of porcelain, and at 

 the other with an index on a dial, upon which the degrees of heat 

 are measured. When used, the instrument is held over the aper- 

 ture of a blast furnace, and the heated air passing through expands 

 the tube longitudinally, and the difference in length as compared 

 with the porcelain standard is indicated on the dial. In a recent 

 experiment, the temperature was registered from Q6'^ F. to 1,200^* F. 

 in less than a minute. 



Heat from Friction. — Mr. Addy exhibited, at a recent meeting 

 of the Massachusetts Institute of Technology, an iron step which 

 had supported a mill-stone weighing 1,200 pounds, and revolving 

 from 100 to 120 times per minute. The shaft was of iron, about 

 2 inches in diameter, surrounded by a ring of hardened steel 

 three-eighths of an inch thick. After running with the above 

 speed for several months, it suddenly broke down, twisted off. On 

 examination the steel and iron were found to be on one side lirmly 



