INTRODUCTION. 9 



reflect that this useful material consisted at one time almost 

 entirely of the delicate stems and leaves of the mosses 

 whose progeny, or rather offshoots, still vegetate on the 

 surface ! Yet such is the case, and recent microscopic ob- 

 servation on the structure of coal from beds of that 

 material stored up for so many ages for the use of man 

 incontestably prove that there the delicate Sjihagnum cush- 

 ioned the swampy ground, and displayed its glossy fruit. 

 The process is no doubt a very gradual one, varying in this 

 respect according to the species which grow in these bogs, 

 and the climate or length of seasons peculiar to the dif- 

 ferent countries in which they abound. A very little exa- 

 mination of the superficial layers of such as are in the course 

 of formation, mil exliibit the appearances indicated in the 

 succeeding remarks. The formation of the bog is ef- 

 fected primarily by obstruction of streams by the fall of 

 trees, through extensive level tracts, as may be inferred from 

 the remains of those found imbedded in them at various 

 depths. Several species of Bryum and Hj/pmwi are the 

 preponderating genera at first, or wdiile the water continues 

 to flow lazily along, but as these decay, and thus increase 

 the obstruction, the Sphar^mim, with its dense spongy foliage, 

 soon makes its appearance and excludes many of its con- 



