58 ADVANTAGES OF GAS. 



how those who have it in their power to obtain these advantages persist in 

 the use of oil and tallow. 



There are some disadvantages attending the use of gas-lights in a close room ; 

 for unless the apartment be well ventilated, an unpleasant heat will be felt, 

 often producing at the same time the effect of sickness and oppressive head- 

 ache. The capacity of ventilators adapted to rooms in which coal-gas is 

 burned should greatly exceed that actually capable of carrying off the heated 

 vapours ; they should be made of tubes, opening from the top of the room at 

 the angles formed by the meeting of the ceiling and sides, and carried into the 

 open air by pipes several feet high, thus causing sufficient draught to ensure 

 perfect ventilation. One pipe may be taken from the cornice over the chim- 

 ney-piece and conducted up the flue, and the end of the tube covered by a 

 hood. An adequate supply of fresh air must of course be ensured from the 

 bottom of the room. Dwelling-houses may thus be illuminated with advan- 

 tage and comfort. 



The comparative effect of heat evolved during the combustion of inflam- 

 mable gases, and other substances capable of burning with flame, will be 

 found in Dalton's System of Chemistry, vol. i. p. 76. 



