492 STEVENSON— THE FORMATION OF COAL BEDS. [Nov. i, 



plane as the roots continues as far as the excavation extends. Lepi- 

 dostrobus variabilis occurs abundantly about the level of the roots, 

 more than a bushel of specimens having been obtained around the 

 trees. A coating of coal, one fourth to three fourths of an inch thick, 

 surrounded the trees, so tender that it flaked ofif and left the stems 

 decorticated ; but some harder coal near the roots of one tree 

 showed the bark fluted longitudinally. The largest tree was ii 

 feet high, 15 feet in circumference at the base and 7 feet and a 

 half at the top. The next in size was 6 feet high, seven and a half 

 feet in circumference and less tapering; the others were shorter. 

 The roots could be followed only a short distance owing to the 

 character of the excavation. They are covered with a thin stratum 

 of coal, 8 to 10 inches thick, which Hawkshaw thinks probably 

 represents the vegetable covering of the place on which the trees 

 stood. 



Binney" says that when erect trees were first found, an attempt 

 was made to refer them to accidents as snags ; but discoveries by 

 Hawkshaw and Bowman, near ^Manchester, aided toward recogni- 

 tion of their growth in situ. During a recent examination of ex- 

 cavations for the Bury and Liverpool railway near Wigan, he had 

 discovered not merely a forest of erect Sigillaria, with roots just as 

 they had grown, but also many Calamites in similar state of preser- 

 vation. The excavation is about 25 feet deep and in a light gray, 

 silty clay very like that at St. Helens and Dukenfield, where the 

 earlier discoveries were made, and the deposit is between two coal 

 beds. In a distance of 50 yards, he found 30 upright trees and 

 some prostrate stems of Sigillaria. They were 2 to 3 feet in 

 diameter, 2 to 12 feet high and filled with silty clay, the bark having 

 been converted into brilliant coal, one fourth of an inch thick. 

 Many Calamites were seen among the trees, 4 to 5 feet high, one 

 to 5 inches in diameter, with a thin coaly crust and filled with the 

 silty clay. Each type occurred in all parts of the deposit from 

 top of the lower seam to bottom of the upper. During a second 



" E. W. Binney. " On Fossil Calamites found standing in an erect 

 Position in the Carboniferous Strata near Wigan, Lancashire," Loud., Edinb. 

 and Dubl. Phil. Mag., Vol. XXXL, 1847, PP- 259-266. 



