PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 571 



The formulae for lampblack and charcoal arc founded on the 

 latest investigations about those substances, proving that they con- 

 tain some very small amount of hydrogen very intimately com- 

 bined. 



The apparent increase in the amount of carbon in this series is 

 simply caused by the entire loss of oxygen and partial loss of 

 hydrogen, taking place during the progress of the chemical 

 changes through which vegetable fibre passes, -when in the pro- 

 cess of combination. 



The following extracts were presented by the Chairman: 



The Fire-Extinguishing Cartridge. 

 The latest invention in France is a sort of cartridge, containing 

 ingredients which are capable of extinguishing fire. This is 

 efltected by the sudden development of a large quantity of hydro- 

 chloric acid gas. The scientific principle has long been known, 

 but it has never been put into a practical form. The cartridges 

 resemble brown paper parcels, and are of two sizes. No. 1 is 

 about eight inches lono; and two and a half inches w4de, and is 

 intended to be thrown by the hand into the heart of the fire. A 

 string is also attached by which it may be projected as from a 

 sling. The cartridge is slightly explosive, so as to scatter the 

 substance producing the extinguishing gas. No. 2, or the second 

 sized cartridges, are simply thrown (the cover being torn ofi" ) into 

 the water of the engines, which they saturate with a substance 

 producing hydrochloric acid gas as soon as the water touches the 

 fire. Experiments have proved that one-tenth of the water that 

 would have been necessary to extinguish a fire is only requisite 

 when the cartridges are mixed with it, and that the saving of time 

 is in the same ratio. They are very inexpensive. 



Curious Experiment. 

 Procure a basin of mi Ik- warm water, throAV into it half-a-dozen 

 pieces of camphor about the size of a pea; they will soon begin to 

 move, and acquire a rotary and progressive motion, which will 

 continue for a considerable time. If now, one drop of oil of tur- 

 pentine, or sweet oil, or even of gin (if allowed on the premises), 

 be let fall upon the water, the pieces of camphor will dart away, 

 and be deprived of their motion and vivacity. Little pieces of 

 cork, that have been soaked in ether, act much in the same way 

 as camphor, when thrown upon water. Camphor, being highly 

 combustible, will burn if ignited while floating upon water, pro- 



