38 STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 



clearly the Dy-gyttja of H. von Post, the Lebertorf of Caspary, the 

 Sapropel-mud of Potonie. 



The salient characteristics of peat deposits are practically the 

 same in all lands and the descriptive terms employed in different 

 languages are almost equivalents ; the German Hochmoor may be 

 regarded as the Heathermoor of Scotland, the tourbiere haute of 

 Holland and France ; the Niedermoor, Rasenmoor, Wiesenmoor and 

 Griinlandmoor are but phases of the bogmeadows, morasses and 

 tourbieres basses of other lands ; and the Waldmoor is a forested 

 bog. Danish students long ago recognized the types under the 

 names of Lyngmose, Svampmose or Hoermose, for the Hochmoor; 

 Kjaermose or Engmose for the bogmeadows ; and Skovmose for the 

 wooded bog. Later German writers in some instances use Hoch- 

 moor, Flachmoor and Zwischenmoor. These several types, where 

 the succession is normal, occur in definite relation to each other, 

 marking successive stages in the growth of a deposit. 



Groivth of Peat Deposits. — The succession of stages in growth 

 of a peat bog was determined in detail more than lOO years ago. 

 All who have visited ponds in process of filling by peat are familiar 

 with the ofttimes concentric bands of differing plant associations 

 around the central water-area. This striking feature was empha- 

 sized by observers at a very early date, but a comparatively recent 

 reassertion of the relation, as bearing on the formation of coal beds, 

 seems to have come as a revelation to some, who had already dis- 

 cussed various questions relating to coal and coal beds. It is at 

 least strange that the literature respecting peat appears to be un- 

 known to so many geologists, since it is not confined to brief notes 

 or to memoirs scattered through publications of learned societies, 

 but includes elaborate treatises, some of them more than loo years 

 old. Many of these appear to be inaccessible in this country, but 

 they have been cited so frequently by writers in Europe that one 

 must believe them readily accessible there. Their existence has 

 been ignored in discussion of coal relations, except where a casual 

 reference enables a writer to show that the credit for an independent 

 discovery does not belong to some later investigator. The facts 



