SaiUn^ and Steam- Vessels. 173 



London, and others, it has been made use of for ventilation, 

 driven by small steam-engines. Even in crowded sailing ves- 

 sels, it would be found a very efficient machine, as described 

 in the Arch. Mag. 1837. It might be still more applicable if 

 constructed to be easily unshipped, and on such a scale as, 

 while the quantity of air drawn off is not too much diminished, 

 it might bo easily worked by relays of a few men. Several 

 important improvements have lately been made on the eccen- 

 tric blowing-fan, such as the proper angle ascertained, and 

 number of the vanes to effect the greatest discharge of air ; 

 and a farther improvement has lately been made by a house 

 in Glasgow (Mechanics' and Engineers' Mag., June 1843), by 

 expanding the capacity of the centre for the better admission of 

 the air. By this simple modification, it is stated the capabili- 

 ties of the fan are found experimentally nearly doubled, while 

 the disagreeable noise attending the working of the common fan 

 is wholly avoided. 



The other plan alluded to in the communication to the 

 Royal Society in 1742, was " the ship's lungs,'' the ventilator 

 of the celebrated Stephen Hales, D.D., F.R.S., Rector of Far- 

 ington, &c. Of the various schemes for ship ventilation in 

 former times, this appears to have been the most successful, 

 and is still well deserving of notice, and of being kept in 

 view, although it is not now in use. Several papers in the 

 Phil. Trans, of last century speak in high terms of its utility 

 on shipboard. In May 1741, Dr Hales' description of his ven- 

 tilator was read before the Royal Society of London. It is 

 mentioned in the Gent. Mag. 1743, as curious, that the same 

 year, 1741, in which Dr Hales brought forward his invention, 

 one of a similar kind was invented by Martin Triewald, Cap- 

 tain of Mechanics to the King of Sweden ; and that the like in- 

 vention should have been made in Stockholm and London is 

 very extraordinary. 



In 1743, Dr Hales published his Description of Ventila- 

 tors,* &;c. In this treatise he notices the ventilator of Trie- 



• A Description of Ventilators, whereby great quantities of fresh air may be 

 conveyed into mines, ships, &c., vol. i., 8vo. London, 1743 ; vol. ii. 1768. A copy 

 will be found in the British Museum. 



