Suggestions for the better Ventilation of 



pumps, which both suck out and force in air by means of three 

 regulators, and are alternately applied to drive air into, or 

 draw it out from, any place assigned, through square wooden 

 trunks which, being made of slit deal, and ten inches wide in- 

 side, are easily portable, and joined to one another without 

 trouble."* Dr D. illustrates his description with notices of se- 

 veral experiments. At every stroke, eleven cubic feet of air was 

 driven in, or aS many sucked out ; if the axis of the cranks 

 turn sixty times in a minute, one man in that time might change 

 a whole cubic space of eight feet ; and by his estimate, a 

 man breathes a gallon, about 287 cubic inches, of air per minute, 

 and a candle, six in the pound, will burn nearly as long in the 

 same quantity. This agrees with modern calculations, at the 

 lowest estimate — 300 cubic inches are contaminated by a man 

 ]>er minute, although Tredgold and others take the quantity 

 at 800 cubic inches, and a single candle alone at 300 cubic 

 inches. These facts go far to prove the necessity of ventilation ; 

 and in experiments made on board ships' lower decks (Philo- 

 sophical Transactions, vol. 47), it is stated that a candle 

 burned 67 grains in thirty minutes, where there had been no 

 ventilation for twenty-four hours ; after six hours'* ventilation, 

 it burned 94| grains in the same time. Combustion could 

 barely be maintained in the former atmosphere. 



If the utility and convenience of Dr Desagulier's hand- 

 pumps realized the description given of them, they might still 

 be usefully employed in the ventilation of the lower parts of 

 ships. Many other mechanical contrivances might be noticed. 

 For instance, the double air force-pump, worked by two or 

 four men, on the principle now in use for diving-bells, which 

 is worked by a lever, upon a standard, on the plan of Dr 

 Hales"* ventilator. Triewald''s ventilator (page 383) was pro- 

 bably on this principle. It may also be noticed here that the 

 success which attends forcing down air, into mines, by means 

 of a fall of water, points out how the foul air, which accumu- 

 lates in the well of a ship, might in a great measure be dis- 

 charged by letting down to and pumping out fresh water 

 from the well. As the use, however, of mechanical ventilators 

 has been generally, and still may be, even when they are re- 



• The machine was cheaply made — the pumps of copper, and crank of iron. 



