1833.] Scientijic Intelligence. 151 



always find the ratio — > 



w w 



Hence, we know also the ratio of the portion of the effects intercepted 



, . , . b—h^ 



which IS 



w — w^ 



By the principles of ratios we must therefore have — > — — — 



w^ w — w^ 

 Or, in other words, the portion of the heat which passes the screen 

 affects the black and white surfaces in a different ratio from that 

 portion which is intercepted. The two portions are thus clearly 

 distinguished by different properties. Or, in other words, the whole 

 effect is due to two distinct causes acting simultaneously ; in which 

 the transmissibility or otherwise is invariably accompanied by the 

 particular relation to surfaces. The one species agreeing in these 

 properties with the solar rays, the other with the heat from non- 

 luminous sources. 



M. Melloni failed, like the author, in his attempts to polarize 

 simple heat. But many of his experiments, and especially this, 

 have been since repeated by Prof. Forbes of Edinburgh, who has 

 succeeded in establishing the polarization, both by transmission 

 through tourmaline and piles of mica, and by reflection, most de- 

 cisively in the heat from luminous sources, and from non-luminous 

 also ; though he allows that in this last case the effect was extremely 

 small. He has also followed out the subject into numerous important 

 consequences. (See Edinb. Trans, vol. xiii.) The distinction de- 

 duced from the experiments of the author (above referred to) must 

 however affect the entire serieis of results relative both to polarization 

 and transmission. 



II. — Application of Hot Air in the smelting of Iron. 



This important improvement is now generally appreciated. At the 

 smelting furnace of Plons in Wurtemberg, before employing the 

 hot air the consumption was 100 kils (2J cwts.) of ore, 40 cubic feet 

 (48i) of charcoal, and the produce under the old system was 3,000 

 kils, (3 '58 tons) while with the hot air it is on an average 3,750 

 kils, (4*48 tons.) At Koningsbronn, in the same kingdom, to ob- 

 tain 108 livres (1*17 cwts.) of bar iron with cold air, it required 20 

 cubic feet (24*2 Eng. c. f.) and with hot air only 17 cubic feet, 

 (20i). {Ann, des Mines, vi. 464.) 



The temperature to which the air is raised, is however much 

 inferior to the lowest standard in this country, for at Plons, accord- 

 ing to Berthier, the temperature of the heated air is only 150'' or 

 200", (302°, 392 ' F.) while at the Clyde iron works, the usual test 

 of the standard temperature is the melting point of lead, or 006° F. 

 This is the lowest point to which the heat is allowed to fall, for it 

 may in general be much higher. Yet even with this disadvantage 

 in Germany, we see that the expenditure of the combustible matter, 

 has been reduced one-fourth, with a sensible increase of the product. 



