hy Ammoniacal Liquor of Coal Gas. 



657 



cubical contents of a horticultural house ; so that the quantity 

 of liquor necessary to fill one fifth or any other portion of the 

 contents of a house, at a mean temperature and pressure, is thus 

 easily known. But all houses are not at a mean temperature ; 

 viz., 60° Fahr. : it may, therefore, be necessary to make a cor- 

 rection in the volume of gas for temperature. The following 

 rule may, therefore, be used to estimate iirhat would be the 

 'volume of any i^ortion of gas, if brought to the temperature of 60° 

 Fahr. : — Divide the whole quantity of gas by 480 : the quo- 

 tient will show the amount of its expansion or contraction for 

 each degree of Fahrenheit's thermometer. Multiply this by 

 the number of degrees which the gas exceeds or falls below 

 60°. If the temperature of the gas be above 60°, subtract 

 the product from, or if below 60°, add it to, the absolute 

 quantity of gas : and the remainder in the first case, or sum in 

 the second, will be the answer. 



As perfect accui'acy in determining the quantity of gas is 

 not necessary, there never can be need of any correction for 

 pressure. 



All this may possibly, to some, appear to have more of 

 craft than utility in it : to which I say, first, if a thing is 

 worth doing at all, it is worth doing rightly ; and, next, if it 

 serves no other purpose, it will be a good exercise of thought, 

 &c., to young gardeners. Now, as to the mode of producing 

 and applying the gas. Those who can, ought to have a vessel 

 proper for the purpose, made of tin, a section of which is 

 here represented, (fg. 126.) 



In this figure, a is a cylindrical vessel of tin, about 15 in. in 

 diameter, and 6 in. deep ; b is a channel, formed by an exter- 

 nal concentric cylinder of tin, about 2 in. deep, and half an 



Vol. VIII. — No. 4rl. uu 



