GEOLOGICAL SURVEY OF THE TERRITORIES. . 185 



Considerations affecting economic value of these coals. 



A coal to be of value in the arts and as a domestic fuel should have 

 certain properties which render it easy of transportation, not easily nor 

 deleteriously affected by weather or climate; should be capable of rapid 

 ignition, and of having its combustion regulated to suit the different 

 circumstances attending its employment; should be capable of raising 

 proportionately to its bulk and weight a large amount of water to the 

 state of vapor, and should contain within itself the least quantities of 

 such substances as by contact with the grate bars at a high heat would 

 injure them, or whose products of combustion are poisonous to vegeta- 

 tion, or to animal life, or are corrosive. 



It follows from some of these conditions that the coal to be of the 

 greatest possible use must neither be crumbly nor so compact and tough 

 > as to render its oxidation difficult by permitting a comparatively small 

 extent of coal surface to be brought in contact with the oxygen of the 

 draught. Also, for the same reasons, it must not cake or run together 

 so as to exclude the air from its interior parts, nor pulverize whereby 

 much loss is sustained by the dust being carried through the flame and 

 up the chimney without being consumed. Then the cleavage of the coal 

 should be such that a large amount can be stored without waste of room 

 in the interstices between the lumps, for it is evident that more material 

 can be packed in a given space when the form of the separate pieces is 

 somewhat regular and the surfaces are close together, than where each 

 lump touches the neighboring lump in only a few points, leaving an un- 

 occupied space between their surfaces. It should be hard enough to 

 resist the grinding and pulverizing effect produced by motion as in the 

 bins of a steamer or the tender of a locomotive. In the article on the 

 subject in Professor Rogers's report on the geological survey of Pennsyl- 

 vania, the author for many reasons leans to the belief that to the many 

 economic purposes the semi-bituminous coals are better adapted than 

 any others. From the blacksmith's forge and the smelting and roasting 

 furnace to the uses of the locomotive or the kitchen, the Eocky Mount- 

 ain coals have been sufficiently proved in the last few years to answer 

 admirably all the requirements made of them. As it is not possible 

 to obtain all these good qualities in any single fuel, (see Eogers's 

 report,) the problem in every case is to select that which possesses the 

 greatest number of them. For instance, for railway purposes the coal 

 of the Eeal Dolores, though containing a higher percentage of fixed car- 

 bon, is less valuable than some of the semi-bituminous coals, because it 

 is neither so easily ignited nor is its combustion so easily regulated, 

 whereas for domestic and all other purposes where the hard dry coals 

 are preferred it is a most excellent fuel. Those coals which disintegrate 

 readily on exposure to the weather, (this includes most of the beds on 

 the eastern flanks of the Eocky Mountains, and in fact the majority of 

 the western coals everywhere,) are not so serviceable to the engine- 

 driver (whatever their percentage of carbon may be) as others with 

 more ash and water but also more power of resistance to atmospheric 

 influences. 



The examination of two samples of brown coal from Wyoming Terri- 

 tory, by the very able chemist. Dr. F. A Genth, of Philadelphia, will be 

 useful for comparison in this connection : 



1. Coal from seven miles east of Cooper Station, on the old stage road, Laramie 

 Plains, Wyoming Territory, gave : 



Per cent. 



Moisture 9. 23 



Volatile matter 39.12 



