162 SCIENCE IN SHORT CHAPTERS. 



but no less effectively, than in these cases. In doing so it 

 maintains a certain degree of warmth about the roots of 

 the plants that grow there, and gradually sets free the solu- 

 ble salts which the rotting vegetables contain, and supplies 

 them to the growing plants as manure, at the same time 

 forming the humus so essential to vegetation. 



A great excess of water, such as soddens the bog, pre- 

 vents this, and also carries away any small quantity of 

 soluble nutritious salts the soil may contain. Thus, in- 

 stead of being warmed and nourished by slight humidity, 

 and consequent oxidation, the bog soil is chilled and 

 starved by excess of water. 



The absolute necessity of the first operation that of 

 drainage is thus rendered obvious; and I suspect that the 

 need of four years' rest, upon which Mr. MacAlister insists, 

 is somehow connected with a certain degree of slow com- 

 bustion that accompanies and partially causes the consol- 

 idation of the bog. I have not yet had an opportunity of 

 testing this by inserting thermometers in bogs under differ- 

 ent conditions, but hope to do so. 



The liming next demands explanation. Mr. Henry says 

 that "it leaves the soil sweetened by the neutralization of its 

 acids." 



In order to test this theory I have digested (i.e., soaked) 

 various samples of turf cut from Irish bogs in distilled 

 water, filtered off the water, and examined it. I find that 

 when this soaking has gone far enough to give the water 

 a coloring similar to that which stands in ordinary bogs, 

 the acidity is very decided quite sufficiently so to justify 

 this neutralization theory as a partial explanation. There is 

 little reason to doubt that the lime is further effective in 

 enriching the soil; or, in the case of pure bogs, that it forms 

 the soil by disintegrating and decomposing the fibrous 

 vegetable matter, and thus rendering it capable of assimila- 

 tion by the crops. 



Another effect which the lime must produce is the 

 liberation of free ammonia from any fixed salts that may 

 exist in the bog. 



The bog-burning method of reclamation is easily 

 explained. In the first place, the excessive vegetable 



