328 Review of Prof. Johnson’s Report on American Coals. 
another table and remarks on the “average reductive powers of 
American and foreign coals as tested by litharge ;’—the ‘foreign’ 
coals referred to consisting of anthracites, free-burning and bitu- 
minous coals of France, tested by M. Baudin. 
The details of the organic analysis of coal from Caseyville, Ky., 
and from the Osage River, Mo., are full and satisfactory, and 
serve to show’the ordeal to which all the others would have been 
subjected, had time and other circumstances permitted. Unfor- 
tunately neither of these two coals was in quantities sufficient to 
be submitted to experiments under the boiler. 
Table CXC, exhibits the “ proportion of the several wasle ma- 
terials from the furnace compared with the weight of fuel burned, 
showing also the composition and density of each material.” The 
next table exhibits the “effect on the evaporative power of the 
unit of combustible matter, produced by closed and open air 
plates at the furnace bridge.” The next the “effect of open air 
plates on the rates of evaporation in the boiler when using differ- 
ent kinds of coal.” But that one which we think the most interest- 
ing and original in its results is the table ‘exhibiting the analysis, 
proportions, and heat-absorbing powers of gases from combustion.” 
These analyses were frequently repeated, as will be seen by refer- 
ence to the column of remarks in the table of daily observations, 
and made during the progress of the bustion of the material in 
the grate, by drawing the gaseous products of that combustion 
directly from the flues. From the data thus obtained, and by a 
series of laborious calculations, based upon the best established 
coéflicients of the specific heat of the several products, the amount 
of the evaporative power of the fuel thus disposed of was calcu- 
lated. This added to the amount rendered efficient in the gen- - 
eration of steam, gives the “total calculated evaporative power to 1 
of fuel from 212°. Wecannot leave this subject without recom- 
mending this table to the careful study of those who may hereafter 
make experiments on this subject. With a well constructed fur- 
nace, stack, and chimney, and an apparatus not very complicated, 
the efficiency of a fuel disposed of in this way may be as satis- 
factorily determined as that which is spent in generating steam. 
The following short table we have constructed from Prof. J.’s 
remarks to convey an idea of the kind of information derivable 
from the experiments on gases just referred to : 
