1 8 INTRODUCTION. 



found in the coal-mine at Planitz near Zwickau, in a working which had 

 been opened six years before but had meanwhile fallen in, a piece of wood 

 several decimetres long which was entirely changed into a dark brown 

 coal. All these alterations Hausmann refers directly to the effect of the sul- 

 phuric acid arising from the pyrites. Even the coals of the Coal-measures 

 may have reached their ultimate condition in a comparatively short time. 

 This is suggested by the remarkable rolled fragments of coal of Commentry 

 and Champagnac les Mines, which have their edges sometimes still sharp. 

 These fragments, the description and bibliography of which will be found 

 in de Lapparent l , are a component part of the Carboniferous conglomerate 

 which lies above and below the coal-seams ; seams of coal must therefore 

 have been in existence at the time when the conglomerates were formed 

 from their erosion and destruction. 



Again, we may compare the lignite-formations in question with the 

 extensive woody swamps along the east coast of N. America from Virginia 

 to Florida. We are indebted to Lyell 2 for a description of one of the 

 largest of these, which lies not far from the sea in the neighbourhood of 

 Cape Hatteras and is known by the name of the Great Dismal Swamp. 

 It is composed of a black pulpy ooze overrun and concealed by a dense 

 tangled covering of low shrubs, in which large trees, chiefly Taxodium 

 distichum and Chamaecyparis sphaeroidea, have taken root. These trees 

 sometimes sink of themselves in an upright position in the ooze, or they are 

 blown down by the wind and fall into it, in which case their woody 

 substance remains in a state of perfect preservation. Great quantities of 

 valuable wood are thus fished out of the swamp. It is a remarkable fact 

 that in consequence of the covering of vegetation which prevents the dis- 

 persion of the waters the middle of the swamp is occupied by a large lake 

 some twelve feet higher than the surrounding land. 



From all the evidence which has been collected up to the present time 

 we may without hesitation refer the formation of the coals of every period 

 in the earth's history, from peat backwards to graphite, not indeed to 

 identical but to analogous processes. It would be going too far to connect 

 them all together in one series of developments and to assume that pit- 

 coal had at first the character of lignite, and that our deposits of lignite 

 would in course of time become coal ; on the contrary, this mode of forma- 

 tion was affected in each particular case by external influences which 

 were different at different times, as is clearly shown by the rolled coal- 

 fragments mentioned above, and by the coals from the lower beds of the 

 Coal-measures of Central Russia which occur in conjunction with true coal 

 and also with deposits resembling lignite. So far we may consider that 

 there is at present a general consensus of opinion. 



1 de Lapparent (1), vol. ii, pp. 842, 866. * Lyell (2), vol. i, p. 142. 



