PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 511 



A New Battery. 

 Mr. ToiTcgiriaiii described before the French Academy of Sci- 

 ences, a new battery. The positive pole of the pile is represented 

 by metallic lead, and the negative by carbon. It contains an alka- 

 line acetate solution, which gives a large quantity of pure carbo- 

 nate of lead [plubmarit), besides electricity, which may be profit- 

 ably emplo3'ed. This is an innoxious method of making white 

 lead, and if economical, when electricity is generated for tele- 

 graphic purposes, it may be of considerable importance. 



Danger in Preparing Acetylene. 

 Dr. Calvert, in a note to the London Chemical News, calls 

 attention to the great danger in preparing formyl or acetylene 

 C2 H. according to Kletinsky process, which is to fuse together 

 under naptha twenty-five grammes of mercury and ten grammes 

 of potassium. The dried amalgam is rubbed to powder and 

 heated in a flask with ten grammes of pure chloroform {eralid), 

 sets free a litre of acetylene {erel). Dr. Calvert states that after 

 gentle heat had been applied for about ten minutes to the mixture 

 of chloroform (eiriltd), and the amalgam of potassium, a terrible 

 explosion occurred, destroying much valuable property, but for- 

 tunately injuring no person in the laboratory. 



Draft of Chimnies. 



During the discussion on ventilation, the chairman submitted 

 the following brief : 



1. The draft of a chimney, or flue, depends mainly on the dif- 

 ference between the temperature within and without. 



2. A tall chimney will increase the draft, because it limits the 

 spreading or lateral action of the products of combustion, keeping 

 them in one straight continuous column, and protecting them from 

 the cooling efiects of the surrounding air. 



3. Too tall a chimney will impede the draft, because the ascend- 

 ing column is impeded by greater friction against the sides of the 

 chimney, and is cooled to a greater extent by radiation from the 

 outside of the chimney. A new and damp chimney, even if short, 

 will absorb the heat in the smoke, thus lesseninj; the draft. 



4. The higher the heat of the smoke, the greater will be the 

 diffejj-ence between the temperature, outside and in, and the greater 

 will be the draft within certain limits. 



5. Too great heat in the smoke will diminish the draft, because 



