22 PYROTECHNY. [l. 



school system, where some hundred thousand children in the 

 United States, breathing a pestilential air, are shrivelled by a 

 parching heat, and doubtless lay the foundation of life-shorten- 

 ing diseases. The remedy should be applied by the architects : 

 but, since few of them have properly attended to this subject, 

 those who engage their services should oblige them to defend 

 us from internal inclemency of the weather by suitable ar- 

 rangements for heating and ventilation, as well as from exter- 

 nal inclemency, in the buildings they construct. Beside the 

 essays of Reid on warming and ventilation, there is a small 

 work in Weale's Rudimentary Series, published in 1850, which 

 may be consulted. On the warming and ventilation of the 

 Lunatic Asylum, Philadelphia, see Journ. Fr. Inst. (3) xix. 270. 



,3. Pyrotechny. 



The discovery of the properties of gun-cotton has led to an 

 attempt to find other compositions to replace gunpowder, one 

 of which we notice. 



A new Cfunpowder. — Augendre has found that a mixture 

 of 1 part yellow prussiate of potash, 1 part white sugar, and 2 

 parts chlorate of potassa, when separately reduced to a fine 

 powder, and then mixed by hand in a wooden mortar, or larger 

 quantities, moistened with 2 or 3 per cent, water, and mixed in 

 a bronze mortar with a wooden pestle, and then granulated 

 and dried in the usual way, will give a gunpowder which is 

 readily fired by contact with an incandescent or lighted body. 

 The mixed powders will act well without granulation. Its 

 advantages are, that it is formed of substances of uniform 

 composition, which are unalterable by dry or moist air ; the 

 powders may be kept separate, and mixed when wanted, and 

 the mere mixture acting like the granulated powder ; the force 

 is greater than that of common gunpowder. Its disadvantages 

 are that it inflames more readily than gunpowder ; and it 

 oxidizes iron barrels so much that its use must be confined to 

 bronze metal. 



Grun-cotton. — According to Marx (Pogg. An. Ixxviii.) the 

 average temperature at which gun-cotton explodes is 199°, if 



