182 _ NEW SOUTH WALES COALS, 
over similar ground to know what processes were employed ; 
and when it is wished to compare results it is often a great 
advantage to be able to use the same methods The proximate 
were made according to the well known process described in 
se 
Crooke’s “Select Methods in Chemical Analysis,” p. 368, in each 
oal 
y 
The specific gravity was determined upon the coal in the form 
of a coarse powder; the powder was allowed to soak in the specific 
gravity bottle, placed in a warm place, until air-bubbles ceased to 
be evolved, when cool the second weighing was proceeded with. 
dina: 
Calculated calorific intensity and evaporative pea 
lated according to the formula given by the same author, Pp. ate 
On examining the two sets of results, 7.e., the cal ra 
intensity and the calculated evaporative power as determined all 
the calorimeter, it will be at once apparent that they do not he 
cases place the coals in thesame order—there is no doubt that o 
things besides the absolute quantities of carbon, hydrogen, nt 
and ash, influence the production of heat and help to a re 
the value of a coal—we as yet really know very little as to ‘ioe 
the combustible elements are combined in coals, or whether a 
are differences in the mode of such combination in different oat 
—it is most probable that there are—but we do know that there 
considerable variations in the mechanical structure of coals, “gr 
must necessarily influence the rate of combustion and the amoun 
heat generated. vessels 
wet is a well-known fact that many command anes, ond tote 
longing to the Royal Navy, the + Mail Com oe: 
Fitenournal lines ates ccutharn to nertheed coal, mo a 
former tai ash, th lisad tage f the gr the 
of ash is considered to be counterbalanced by the ee: but 
southern coal burns uniformly and does not form a aif orther® 
when it is desired to get up steam rapidly, then the 
is preferred, 
