MECHANICS AND USEFUL ARTS. 75 



THE BENEFICIAL EFFECTS OF SMOKE. 



A writer in the London Times argues in favor of the sanitary effects of 

 smoke. He says that smoke, being nothing more than minute flakes of 

 carbon or charcoal, the carbon in such a state is like so many atoms of 

 sponge, ready to absorb any of the life- destroying gases with which it may 

 come in contact. In all the busy haunts of men the surrounding air is, to 

 a certain extent, rendered pernicious by their excretions, from which invisi- 

 ble gaseous matter arises, such as phosphuretted and sulphuretted hydro- 

 gen, cyanogen and ammoniacal compounds, well know by their intolerable 

 odor. Now, the blacks of smoke (that is, the carbon) absorb and retain 

 these matters to a wonderful extent. Every hundred weight of smoke 

 probably absorbs twenty hundred weight of the poisonous gases emanat- 

 ing from the sewers and from the various works where animal substances 

 are under manipulation. 



SELF-ACTING DRAFT-CLOSER. 



A simple and effective apparatus has been devised by Professor Tread- 

 well, of Cambridge, for regulating the draft in ordinary hot-air furnaces. 

 This apparatus acts by the expansion of the furnace itself, so that, when- 

 ever the combustion is established and carried to a certain point, the 

 expansion that must attend that state of the combustion moves a catch, 

 and the damper closes with absolute certainty. The contrivance is as sim- 

 ple as an old-fashioned door latch, and no more likely to get out of order. 



COOKERY FOR SOLDIERS. 



A new method of cooking and heating, the invention of General 

 Dembinski, has recently been introduced into the French armies. The 

 principle of the invention is very simple, but the applications of it are 

 numerous. A cylinder made of zinc, copper, sheet iron, or any other 

 metal, with an inner cylinder containing sand or small stones, is connected 

 by means of two tubes with a very small vessel, which is placed on a fire, or 

 over a gas light or a lamp. The space between the two cylinders, which 

 is small, is filled with cold water. The vessel on the fire, which is mode 

 of very thin metal, is filled with water, which boils almost immediately. 

 As the water boils it rushes by one of the pipes to the cylinder, and by 

 the other pipe the water in the cylinder returns to the vessel over the fire, 

 and this process goes on until the whole of the water boils, which is in 

 one-fourth of the time that would be required to bring it to the boiling 

 point if placed in a large vessel over the fire in the usual way. The pro- 

 cess is continued until the sand or stones in the inner cylinder have 

 become perfectly heated. Two cocks, close to the cylinder, are then 

 turned, and the pipes being unscrewed, the cylinder is carried by means of 



