Prof. C. H. Hitchcock— The Coal Area of the U. States. 99 



City, and have been in my collection since 1866. The transition 

 from silicified wood to silicified lignite was exceedingly gradual, one 

 end of the log being black with a somewhat hackly fracture, while 

 the colour of the other end was yellowish- white, and its fracture 

 conchoidal ; both distinctly retained their original woody structure. 



These results of analysis show that although every trace of organic 

 matter has disappeared in the silicified wood, the silicified lignite, 

 produced from the same tree, still retains about 14 per cent, of carbon. 



It will likewise be observed that if, in the second analysis, ab- 

 straction be made of the carbonaceous matter, and the per-centages 

 be re-calculated, they will very nearly agree with those of the 

 eilicified wood. 



In both analyses the amount of potassa found is greater than that 

 of soda. 



III. — The Coal Area of the United States op Ameeioa. 

 By C. H. Hitchcock, Hanover, N.H., TJ.8.A. 



IN compiling for the Census Bureau of the United States a small 

 geological map, I had occasion to determine the precise areas 

 occupied by workable beds of Carboniferous Coal. As the sum 

 total is different from that recently stated in the Geological Maga- 

 zine,^ I have thought a correction desirable ; and present a few 

 statements, based upon original authorities, the best within my 

 reach. 



There are eight distinct areas of the Coal Measures in the United 

 States. They are — 1. The New England Basin. 2. The Pennsyl- 

 vania Anthracite. 3. The Appalachian Basin. 4. The Michigan 

 Basin. 5, The Illinois Basin. 6. The Missouri Basin, 7. The 

 Texas Basin. 8. Areas of unknown extent, probably inconsiderable, 

 in the Eocky Mountain Eegion. 



1. Neio England Basin. — This is in Massachusetts and Ehode 

 Island, estimated to cover 750 square miles. The coal is a plum- 

 baginous anthracite, used to advantage in some smelting furnaces. 

 Perhaps eleven beds exist, best seen in Portsmouth, E.I. Their 

 maximum thickness is 23 ft. The Coal Measures are about 2,500 

 feet thick.^ 



2. Pennsylvania Anthracite. — This is the most important coal 

 district in the United States. Including the Broad Top semi-anthra- 

 cite, of 24 square miles, the five separate basins amount to 434 

 square miles. The Measures are from 2,000 to 3,000 feet thick. 

 The number of distinct beds varies from two to twenty-five, ac- 

 cording to the depth of the basin. The maximum thickness at 

 Pottsville is 207 feet, while the average cannot be far from 70 feet.* 



3. Appalachian Basin. — This occupies an area of 63,475 square 

 miles, extending from Pennsylvania to Alabama, all of bituminous 

 coal. 



1 Geol. Mao., Vol. IX., p. 236. Said to be 100,528 square miles. 



2 Geology of Island of Aquidneck, by C. H. Hitchcock. Proc. Amer. Ass. Adv. 

 Set., 1860. 



* Geology of Pennsylvania, by H. P. Rogers. 



