GRANITE. — LIME. 
347 
ing to the place and manned by her own citizens ; 
and of these vessels Dr. Jackson states that more 
than 100 are constantly employed. The measure 
of a lime-cask is fixed by law at 40 gallons, and 
they hold 300 lbs. of lime. A kiln capable of burn- 
ing 300 casks of hme is 14 feet long, 14 feet high, 
and five feet deep. It has three pointed arches,* 
that in the centre being five feet high. The kilns in 
Maine are usually buill of talcose slate. 
Lime is burned very extensively on the Hudson 
River, particularly at Barnegat, where the kilns are 
kept constantly burning from the opening of the 
river in the spring until the closing of it in winter, 
without allowing them to cool. The method pur- 
sued here is, after the kiln is once kindled, to charge 
about half a ton of anthracite coal, broken to the 
egg size ; then 300 to 350 bushels of Hmestone, in 
lumps of 20 to 30 pounds each ; and at the end of 
12 hours another charge of coal and limestone, and 
so on till the kiln is filled. They then draw out 
about 850 bushels of lime from the bottom, and in- 
troduce another charge of coal and limestone, and 
every 12 hours this process is repeated. This oper- 
ation is continued for months, as in a furnace for 
smelting iron. A great economy is thus introduced ; 
the kilns being always kept heated, and the heat 
which would escape in the common mode of man- 
ufacture is here expended in heating other portions 
of limestone, and preparing it for the high tempera- 
ture necessary to expel the carbonic acid. About 
700 bushels of lime are thus obtained daily from 
each kiln, with the consumption of a little less than 
* " There are many improvements," says Dr. Jackson, " to 
be made in the method of burning lime, and one of these con- 
trivances consists in having lateral arches, in which the wood ot 
coal is consumed, while the flame and current of heated ail? 
draw through the limestone, and keep it constantly red-hot. It 
is then, when sufl[iciently burned, drawn out, and more rock is 
to be added to the top of the charge." 
