OF ARKANSAS. 133 



properties observed by experiments on this coal by Johnson, to be very 

 nearly the same as those that would be found in the Spadra coal, if sub- 

 jected to the same tests ; I, therefore, subjoin some of the most important 

 characters representing the efficiency of that coal, compared with Pitts- 

 burg coal ; one of the best known and most generally useful of our western 

 bituminous coals. 



While one part of Pittsburg bituminous coal will generate 8.2 pounds 

 of steam at a temperature of 212 deg., the same quantity of Lyken's valley 

 semi-anthracite, will generate 9.46 pounds of steam at 212 deg. 



While one cubic foot of Pittsburg coal will generate 384 pounds of 

 steam, one cubic foot of Lyken's valley semi-anthracite will generate 459 

 pounds of steam. 



The reducing power of semi-anthracites is considerably greater than 

 that of bituminous coal ; as is shown by the relative amounts of litharge 

 reduced to lead by these same coals: 28.89 parts being reduced by Pitts- 

 burg coal, while 32.6 are reduced by the same quantity of Lyken's valley 

 semi-anthracite. 



The Spadra coal resembles still more closely the Zerbe's run coal of the 

 Shamokin coal field of Pennsylvania, as will be seen by the annexed com- 

 parative approximate analyses : 



Spadra. Zerbes run. 



Volatile combustible matter, 7.90 7.31 



Fixed carbon, 85.6 84.25 



Ashes, 6.0 6.11 



Hayes and Eogers estimate the water evaporated at 212 deg., by 1 pound 

 Zerbe's run coal, at 9.58 pounds. The rate of evaporation per hour, to one 

 square foot of grate, is 88.92, while the average for bituminous coal is 70.92 

 under the same circumstances. 



The combined evaporative power and speed for the Zerbe's run semi-an- 

 thracite are represented by the numbers 4777.4, while taking equal bulks 

 of the averages of bituminous coals, under the same circumstances, the 

 numbers would be 3456.0. 



These semi-anthracites burn after the manner of the natural coke of 

 Virginia, throwing out, when fully ignited, an intense heat, accompanied 

 by a blue flame. 



They require, it is true, a tolerably strong draft to bring them into full 

 combustion, and, therefore, are perhaps not so suitable for open grates as 

 the more inflammable bituminous coals, requiring usually the addition of 

 blowers to increase the current of air passing through the grate, until the 



