130 BOARD OF AGRICULTURE. 



of the smaller forms of vegetation, as grasses, leaves, and 

 moss. Of all the various forms which have contributed to 

 our muck-beds, the spongy mosses constitute, undoubtedly, 

 the most imjiortant constituent. 



THEIR AGE. 



How long a time it requires to form a well-advanced muck- 

 bed is not certainly known ; but under ordinary conditions 

 a hundred centuries may be required, or even five times that 

 number. The stage of decay in which it is found does not 

 always indicate the lapse of time consumed in the clianges ; 

 as, under favoring conditions of extreme heat, or access of 

 air during frequent low stages of water, the changes proceed 

 much more rapidly. It is probable that no muck deposits on 

 our farms, suited to agricultural uses, can have existed, in 

 their lower strata, less than the time which, according to the 

 Mosaic record, man has existed upon the earth. 



DIFFERENCES IN MUCK. 



When these deposits are carefully examined by the eye, 

 they present very marked and important physical differences. 

 In texture and color no two can hardly be said to be exactly 

 alike. Some kinds consist almost entirely of the withered 

 remains of plants which have undergone but little alteration, 

 except mechanically ; in other varieties the organized struc- 

 ture of the plant remains more or less distinctly visible ; in 

 other kinds there is no obvious indication of plant-structure 

 existing. In the latter variety nothing remains but a black 

 unctuous mud, which, when dried, crumbles to a fine dust. 

 I have sometimes found this form of dried muck to be denser 

 than water, having a specific gravity as high as 1.23; but 

 generally it is lower than water, not rising higher than ..88. 



POND MUD, ETC. 



It is not necessary, perhaps, to make further lines of dis- 

 tinction in low-meadow deposits. As regards pond sedi- 

 ments, they belong to a distinct class of waste vegetable 

 material, although identical often, so far as the organic con- 

 stituents go, with bog deposits. 



Three forms of meadow deposits have been pointed out. 

 Those of the first class may be called the "immature forms," 



