284 DR. ANGUS SMITH ON PEAT. 



water containing air, its change may be arrested com- 

 pletely. A certain openness of structure is necessary for 

 the formation of true black peat. 



(( I need not speak of the matter, excepting in relation to 

 the subject of antiquities. If these notions are correct, we 

 may have from ten inches to thirty inches of open fibrous 

 peat in a century, according to the nature of the water 

 supplying the moss. If the supply of water is abundant 

 and easy, and if the water itself is well supplied with 

 earthy salts, we can see no necessary limit to the depth 

 which peat may attain during long ages. If there be a 

 plain, and if the plants are obliged to obtain their inor- 

 ganic salts by capillary attraction or osmose, or by the 

 dialytic action of the peat, then a natural limit must take 

 place. It will not be a sharp line ; but the early peat will 

 grow very fast, and the later slowly, until it ceases to 

 increase in depth. We must therefore judge very differ- 

 ently of different mosses. One may have remained of the 

 same thickness for an indefinitely long time, being as thick 

 in much of the prehistoric as in historic days ; another 

 may have grown about two feet in a century. This latter, 

 however, will not, in all probability, have attained the 

 black stage at w r hich the richer hydrogen compounds are 

 found. At present we have no guide to the length of time 

 required for this stage. 



" When people speak of the age of peat as being exces- 

 sively great, they ought to mention the quality of the peat. 

 If black, we may allow at present very great antiquity, 

 until we learn better ; if covered over from air, we may allow 

 a great age, even to fibrous peat ; if otherwise, there seems 

 no necessity for speaking of a very great age. By follow- 

 ing up this inquiry, which I know to be imperfect, but new, 

 at least to me, we may arrive at some more definite ideas. 

 As an extreme one, I may consider that less than a cen- 

 tury cannot be allowed to thirty inches of fibrous peat, and 



