and when the vessel is cool, the coal is removed
and weighed. In case a platinum crucible is employed, it should have a
tight-fitting cover, and when gases cease to escape, the crucible is
quickly cooled by placing it in cold water.

Coal, or coke, includes of course the ash of the peat. This, being
variable, should be deducted, and the _ash-free coal_ be considered in
comparing fuels.

5.--The _density_ of peat-fuel may be ascertained by cutting out a block
that will admit of accurate measurement, calculating its cubic contents,
and comparing its weight with that of an equal bulk of water. To avoid
calculation, the block may be made accurately one or several cubic
inches in dimensions and weighed. The cubic inch of water at 60 deg. F.,
weighs 252-1/2 grains.

FOOTNOTES:

[10] The apparent specific gravity here means the weight of the
mass,--the air-filled cavities and pores included--as compared with an
equal bulk of water. The real specific gravity of the _peat itself_ is
always greater than that of water, and all kinds of peat will sink in
water when they soak long enough, or are otherwise treated so that all
air is removed.

[11] The "full" cubic foot implies a cubic foot having no cavities or
waste space, such as exist in a pile, made up of numerous blocks. If a
number of peat blocks be put into a box and shaken together, the empty
space between the more or less irregular blocks, may amount to 46 _per
cent._ of the whole; and when closely packed, the cavities amount to 30
_per cent._, according to the observations of _Wasserzieher_.
(_Dingler's Journal_, Oct., 1864, p. 118.) Some confusion exists in the
statements of writers in regard to this matter, and want of attention to
it, has led to grave errors in estimating the weight of fuel.

[12] The _waste space_ in peat and wood as commonly piled, is probably
included here in the statement, and is usually about the same in both;
viz.: not far from 40 _per cent._

[13] See note on the preceding page.

[14] _Der Torf, etc._, S. 43.

[15] See page 00.

[16] On account of the great convenience of the decimal weights and
measures, and their nearly universal recognition by scientific men, we
have adopted them here. The gramme = 15 grains; 5 degrees centigrade = 9
degrees Fahrenheit.

[17] Pliny, Hist. Nat. (Lib. XVI, 1) expresses his pity for the
"miserable people" living in East Friesland and vicinity in his day, who
"dug out with the hands a moor earth, wh