132 
Improved Kilns for hurnvKj Lime. 
acre, may contain from 2 5 to 3 parts, or even more, of nitrogfen. 
as nitrates and nitrites, per 100,000 parts of water. Assuming 
that only 2 5 parts of nitrogen were so carried beyond the reach 
of roots for every 100,000 parts of water passing downwards, 
there would still be, for every inch of rain so passing, a loss per 
acre of between 5 and 6 lbs. of nitrogen, supplied in manure 
at a cost of not much less than Is. per lb. 
The above estimate of quantity must be undei'stood to be- 
adopted only provisionally, and by way of illustration. It is, 
however, a sufficiently near approximation to what must happen 
in the case of many soils and seasons at any rate, to show the 
very great importance of further investigating the reactions of 
various descriptions of nitrogenous manure on different descrip- 
tions of soil, and of determining the best modes, and the best 
periods of the year, for the application of such manurial matters, 
so as to reduce the loss by drainage to a minimum. This subject 
is now receiving attention at Rothamsted. 
Hotliamsted, January, 1871. 
VI. — Description of Ordinary and Improved Kilns for Burning 
Lime for Agricultural Purposes. By Chakles TurnE'I, C.E. 
Prize Essay. 
I. The Common Perpetual Kiln. 
A KILN for burning lime, for agricultural purposes, is generally 
placed in the side of a chalk or limestone hill, to avoid expense 
in brickwork or masonry. The kiln itself, in its cheapest form, 
is an inverted truncated cone from 12 to 15 feet in diameter at 
the top, excavated out of the chalk or limestone rock, and lined 
on the inside with good hard bricks, capable of withstanding a 
considerable amount of fire. The lining should be from 1\ to 
2 bricks thick, according to the size of the kiln, and filled in 
solidly at the back with hard chalk or limestone, set in mortar. 
In the best kilns of this construction, the side walls are built 
upright for about 4 feet in depth, and then the cone is gradually 
tapered off to a diameter of 3 feet at the draught or draw-hole. The 
height of the cone is generally equal to the diameter at the top. 
An arched opening is constructed in the exterior wall in front 
of the ash-pit, which should be sufficiently high to allow of a man 
standing upright, in order that he may get conveniently at the ends 
of the fire-bars when the lime is required to be drawn. Two 
strong cast-iron bars, called bearing-bars, 3 in. by 2\ in., are fixed 
into the brickwork in such a manner that they can readily be 
withdrawn when required : upon them lie the wrought-iron fire- 
bars (which should be circular in section, for a reason which I- 
