146 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



who, in his studies, has endeavored to exchide the influence 

 of radiation, and has made measurements by means of tlie 

 thermo-electric multiplier. He finds that the stones consid- 

 ered by him are much better conductors of heat when wet 

 than when dry, and that various classes of stones, such as 

 marble, sandstone, granite, etc., have approximately the same 

 co-efiicients of conduction, while bricks of all kinds are much 

 worse conductors than the natural stones. 



CHANGE OF TEXTURE IX SANDSTONE BY HEAT. 



According to Mr. John Young, the sandstone bottoms of 

 iron furnaces assume, from the long-continued action of heat, 

 a distinctly columnar form, the old lines of stratification be- 

 ing obliterated, thus showing that heat, as well as electricity 

 and mechanical force, was an agent in the production of the 

 columnar form of rocks. 15 A^ JVbvember 20, 676. 



ANTIQUITY OF THE BURNING MIKEOK. 



Buchwalder states, in reference to the burning mirror re- 

 cently invented by Mouchot, that it was used as long ago as 

 in the days of Numa Pompilius, in whose reign the priests 

 in the temple of Vesta, according to Plutarch, employed a 

 conical reflector, with a solid angle of ninety degrees, as a 

 mirror for concentrating the rays of the sun, thereby pro- 

 ducing the heat necessaiy to light the sacred fires. 



OBSERVATIONS UPON RADIOMETERS. 



Mr. H. A. Carrington communicates to the Popular Science 

 Review a slight contribution in the way of experiments with 

 radiometers, in which he has arrived at the following conclu- 

 sions: First. That when the radiometer is receivinoj lioht or 

 heat, being at a lower temperature than its surroundings, re- 

 pulsion of the black disks must ensue, and continue until the 

 temperatures are equalized. Second. When the radiometer 

 is radiating heat, being at a higher temperature than its sur- 

 roundings, attraction of the black disks, or the apparent re- 

 pulsion of the white disks, must ensue, and continue until the 

 temperatures are again equalized. Third. Ko source of light 

 can produce repulsion of the black disks unless it is capable 

 of raising the temperature of the residual air within the 

 globe. Popular Science Beview, April, 1876, 137. 



