310 Review of Prof. Johnson’s Report on American Coals. 
Art. VIIL—A Report to the Navy Department of the United 
States on American Coals, applicable to Steam Navigation 
and to other purposes ; by Prof. Waiter R. Jounson. 
Tur area of the various coal basins embraced within the terri- 
tory of the United States, is probably greater than that of any 
other of the civilized nations of the earth. Since the application 
of steam as a motive power, this mineral fuel has become an im- 
portant element of national prosperity, and within a few years 
has assumed a prominent position among the materials of national 
defence. As might be expected in so vast an extent of territory, 
a corresponding diversity of character exists in the coals of the 
United States. From the plumbaginous anthracites of Rhode 
Island and Massachusetts they shade off to the highest bituminous 
character. Common observation indicated a corresponding differ- 
‘ence in applicability, and to some extent in the calorific powers 
of the coal in these various conditions. Chemical analysis had 
in some instances shown their elementary differences. But no 
systematic and authoritative examination, of a kind from which 
general pract be deduced, had been performed 
up to the time at which the investigations embraced i in this Re- 
port were commenced. Such examinations, highly important to 
individual interests, were absolutely necessary in a national point 
of view. The steam vessels of the Navy are exposed to the per- 
formance of various duties, in the course of which it is often 
necessary to replenish their exhausted fuel at different stations. 
The best informed engineer would be often embarrassed in his 
operations by the difference in the character of the coals he would 
nd at these stations, and thus endanger the success of the best 
concerted cruise or system of operations. This is peculiarly liable 
to occur in the coast service of the United States. Along the 
northern and eastern Atlantic coast the anthracites are most used, 
while in the Gulf of Mexico the bituminous coals of the Missis- 
sippi valley must be depended upon. A long life of practical 
operations would not give the engineer the same facility of adapt- 
ing his engines to these differences, as he would be enabled to 
obtain by the study for a few weeks of such experiments as those 
detailed in this Report. 
