498 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



sis and by experimental data, establishes the following law : 

 The quantities of water evaporated by consecutive equal 

 lengths of tubes diminished in geometrical progression, if 

 the distance from the source increased in arithmetical pro- 

 gression ; from which it follows that the ratio between the 

 quantities of water evaporated by consecutive equal lengths 

 of tubing is a constant number. The point at which this 

 law begins to prevail is that at which the radiation of heat 

 from the fuel ceases, where heat is communicated to the 

 water by conduction alone. And it appears from observa- 

 tions that in locomotive boilers the evaporation diminishes 

 by nearly one half at each interval of one meter, or from 

 yard to yard ; in other words, the constant ratio is one half. 

 For large boilers, Havrez concludes that the value of the 

 ratio varies between 0.5 and 0.7, but for very small boilers 

 it may fall below 0.5. Proceedings of Institution of Civil 

 Engineers, XXXIX., 398. 



CARBONIC ACID FOE EXTINGUISHING FIEES IN MINES AND 



ON SHIPS. 



The problem of the best method of extinguishing fires in 

 coal-mines and on shipboard seems likely to have received 

 a practical solution in recent experiments at the Torpedo 

 Station at Newport, Rhode Island, as communicated to the 

 American Chemist by Lieutenant Barber, of the Navy, who, 

 after a careful consideration of the subject, is decidedly of 

 the opinion that liquefied carbonic-acid gas is the only sat- 

 isfactory, while at the same time perfectly efficient applica- 

 tion. 



His plan for treating fires on shipboard is to have a flask 

 or flasks, about three feet in length and one foot in diam- 

 eter, at some suitable locality on the spar-deck or elsewhere, 

 containing about one hundred pounds of the gas in a liquid 

 condition. From the top or upper side of the flask a small 

 iron pipe is to be permanently fitted along the water-ways 

 (or just under the main-deck) throughout the entire length 

 of the ship. From this main pipe, at suitable intervals, are 

 branch pipes at right angles to the main, passing down next 

 the skin to every store-room and. hold of the ship ; so that 

 each compartment of the vessel shall have its own pipe or 

 pipes, reaching from its bottom to the main pipe at the spar- 



