MECHANICS AND USEFUL ARTS. 67 



in ice. The value of the felted boxes from a sanitary point of 

 view is to be found in the possibility of providing poor mechanics 

 and laborers with warm food. By portable contrivances it will 

 be easy to keep food warm for some hours, and the advantages 

 to poor workmen cannot be overestimated. To the rich it also 

 insures thoroughly cooked food, while even by them the economy 

 will not be despised. At the Paris Exhibition of 1867 these 

 felted boxes in the Norwegian department attracted a good deal 

 of attention. They were shown in actual operation, and an op- 

 portunity was afforded of tasting food that had been kept in them 

 for some hours." 



CAST-IRON STOVES. 



At a recent meeting of the French Academy of Science, a 

 report was presented from the committee appointed to inquire 

 into the alleged insalubrity attending the use of cast-iron stoves. 

 Extensive experiments had been made, and the results arrived at 

 were, first, that all heating apparatus made of metal, and all 

 stoves made of cast iron, give off, while in use, a large quantity 

 of carbonic acid ; second, that the quantity of that gas given off 

 from stoves of plate iron was often insignificantly small ; third, 

 that the carbonic acid contained in the air was readily converted 

 into carbonic oxide, by coming into contact with thoroughly red- 

 hot stoves ; and, fourth, that the oxide of carbon thus generated 

 may, especially in confined localities, become very injurious to 

 health. To obviate all bad effects, the committee recommend 

 that cast-iron stoves be lined inside with fire-brick, and enveloped 

 outside with a casing of sheet iron, so arranged as to leave space 

 for free circulation of air in communication with a well-drawing 

 chimney. 



BARON LIEBIG " ON A NEW METHOD OF BREAD-MAKING." 



Baron Liebig has just made some important researches on a 

 new method of bread-making. He remarks on the stationary 

 character of this art, which remains to the present day much in 

 the state in which it was thousands of years ago. He dwells upon 

 the sanitar}^ importance of the mineral constituents of grain, and 

 the necessity of a sufficiently abundant supply of them in bread. 

 These are best found in certain kinds of black and brown bread, 

 which are, therefore, more wholesome than the white bread that 

 is nevertheless preferred by most people (especially by the lower 

 orders), on account of its better apjiearance and superior palata- 

 bleness. The problem has hence arisen, how to provide a beau- 

 tiful white bread which shall contain all the essential mineral 

 constituents of black bread. These mineral constituents (phos- 

 phate of potash, lime, magnesia, and iron) are introduced into 

 the bread by the use of the baking-powder invented by Professor 

 Horsford, of Cambridge, in Nortli America. This baking pow- 

 der consists of two powders, — the one acid, the other alkaline. 

 The acid powder is phosphoric acid in combination with lime and 

 magnesia; the alkaline powder is bicarbonate of soda. Two 



