STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 59 



so distinct in ordinary peat as to attract the attention of a casual 

 observer. Under pressure, however, the structure is well-defined. 



Spring*^'' tested the effect of compression on Holland and Bel- 

 gian peat, mature but retaining much material showing organic 

 structure. Under pressure of 6,000 atmospheres, this was changed 

 into a black, brilliant block, with all the physical aspect of a coal ; 

 the fractured surface, as seen under the glass, was distinctly lami- 

 nated, while evidence of organic texture had disappeared. Under 

 this pressure, the peat became plastic and ran out into the chinks of 

 the compressor. Thoroughly matured peat, after this compression, 

 does not absorb water and does not return to its original form. 

 von GiimbeP^ subjected spongy sphagnum-peat to a pressure of 

 6,000 atmospheres, by which it was rendered apparently homo- 

 geneous and as hard as pasteboard. A pressure of 20,000 atmos- 

 pheres increased the density to that of sole leather. In each case, 

 lamination was distinct and the streak was lustrous, but when 

 placed in water, the material swelled to almost the original bulk. 

 Evidently, pressure of brief duration suffices to produce permanent 

 physical change in well-matured peat though not in the immature 

 substance. But one is not dependent on laboratory results ; the 

 experiment has been performed in nature many times and on a 

 grand scale. 



Forchhammer,*'^ in his descriptions of dunes on the Baltic coast, 

 of Denmark, states that among those dunes are numerous lakes 

 and ponds characterized by abundant vegetation and by formation 

 of peat. When an unusual storm passes over the dune, sand is 

 blown into the ponds and puts an end to growth of peat. This 

 buried peat, known as Martorv, is exposed when currents cut away 

 the coast. The phenomenon is not confined to the mainland ; on 

 the north side of Seeland, there was a pernicious stretch of quick- 

 sand early in the eighteenth century but, before 1760, it had become 



^^ W. Spring, " Recherches sur la propriete que possedent les corps soHdes 

 de se souder par action de la pression," Bull. Acad. Roy. Bclg., II., Vol. 49, 

 1880, pp. 367, 368. 



6" " BeitrJige," etc., pp. 127, 128. 



^s G. Forchhammer, " Geognostische Studien am Meeres-Ufer," Ncucs 

 Jahrbuch, Jahrg. 1841, citations from pp. 13, 14. 



