254 EFFECT OF VARIOUS MANURES UPON 



4th. 1 lb. of hydrogen will melt 320 lbs. of ice. 



Authority, Dalton. 

 , , , , 295 lbs. , , 



Authority, Lavoisier. 

 ,, , , 480 lbs. , , 



Authority, Craivford. 



Now, according to the 1st, the relative elementary weight of 

 mineral coal will be 



Carbon, 24, weighing • • . 144 



Hydrogen, 13 „ . . . 13 



Oxygen, 1 „ ... 8- 



165 



And if (4th) 1 lb. of hydrogen be sufficient to melt 320 lbs. of 

 ice, the proportion of the 62^ lbs. melted by the hydrogen con- 

 stituents of the coal will be as 165 : 320 : : 13 = 25 lbs. 



In the case of coking coal, less heating effect is due to the 

 hydrogen portion of its composition, because it contains a less 

 proportion of this element. Calculating from Liebig's analysis 

 (2), the hydrogen it contains ought to melt 21 lbs. of the 62^ 

 melted by the combustion of this kind of coal. Or the hydrogen 

 in the composition of coking may be said to produce one- third of 

 the lieating effect, and the carbon two-thirds. 



The experiment with this boiler has proved the truth of what 

 is stated by Tredgold with reference to fire-places — "There 

 should be no more iron-work about them than is absolutely 

 necessary:" and according to Morveau, as quoted by Tredgold, 

 " the fire-place ought to be isolated from all bodies that aro 

 rapid conductors of heat." 



The apparatus in question is constructed on a principle the 

 very reverse of that pointed out by the above maxims. It can 

 only be applicable in the case of engines where a strong fire is re- 

 quired to be constantly kept up. The inventor was perhaps not 

 aware that for horticultural purposes a slow and prolonged com- 

 bustion is also necessary. 



XL. Experimental Inquiry into the comparative effect of va- 

 rious Manures upon Kitchen Garden Crops. By Mr. R. 

 Thompson, Superintendent in the Orchard and Kitchen Gar- 

 den Department of the Society's Garden. 



I. Asparagus. 



The soil in the Garden of the Society is not so sandy and 



friable as that which is found to produce almost naturally the 



finest Asparagus. In 1843 it was considered advisable to try 



the eflfects of various artificial manures for the growth of this 



