500 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



bicarbonate of soda, and the supply of gas is quite limited ; 

 and, before the machine can be used again, it must be cleaned 

 out and re-charged. One pound of the liquid is equivalent 

 to about eight cubic feet of pure gas ; and any quantity can 

 be carried, as already stated, and kept indefinitely for time- 

 ly use. 



Until lately the use of liquid carbonic-acid gas, on a large 

 scale, has been prevented by two difficulties : first, the want 

 of an apparatus capable of producing a large quantity in 

 a short time and at a low cost; second, the want of suit- 

 able vessels to contain it at low temperatures. Mr. W. N". 

 Hill, chemist of the Newport Torpedo Station, has devised 

 an apparatus, now in successful operation, which produces 

 forty pounds of liquid gas per hour, at a cost of only fifteen 

 cents per pound. To contain the gas Mr. John Matthews 

 manufactures steel flasks of about the dimensions mention- 

 ed, which weigh but little over three hundred pounds, and 

 w T hich have frequently been tested to two thousand pounds 

 per square inch, hydraulic pressure. These are made of 

 sheets of steel rolled up one within the other, the outer one 

 being riveted, while all spaces between the sheets are filled 

 with pure tin. Thinner flasks, consisting of only one thick- 

 ness of one sixteenth of an inch of sheet steel, are made by 

 Mr. Matthews for soda-water purposes. They are carried 

 constantly about the city of ISTew York, and not one, so far, 

 has burst. 



Lieutenant Barber states that Mr. Hill is about publishing 

 a work which will give a full description of the manner of 

 preparing the gas and of applying it; as also the method of 

 forming the flasks and fitting them for the required applica- 

 tion. 



It is quite probable that this principle will, in time, be 

 adopted for extinguishing fires in burning buildings, as 

 more effective in quicker time, and involving no damage 

 from Avater. 7 2>, May, 395. 



SUCCESSFUL SCIENTIFIC BALLOONING. 



The French Society for aerial navigation decided that its 

 programme during 1875 should consist principally of two 

 aerial voyages with the aid of the balloon Zenith, containing 

 three thousand cubic meters, the first voyage to be of long 



