Ohservatioyis on Liebig's " Organic Chemistry. ^^ 119 



streamlets, where motion is kept up in the water, that they will 

 thrive. The tendency of stagnant water to putrescence, and 

 consequently rotting of the roots, will also have its effects. The 

 only plant, he says, that thrives well in their marshy ground, is 

 the spruce fii-; it throws out its roots along the surface, where 

 they will be constantly exposed to the air and ox^^gen, and does 

 not dip the roots into the stagnant water in the soil, as the others 

 do ; so much so, that they can be uprooted with very little 

 trouble. 



When on the subject of these plantations, I may mention 

 the great effects produced from the warmth and shelter they af- 

 ford ; corroborating the statements on these subjects so forcibly 

 made of late in the Quarterly Journal of Agriculture^ of the 

 great benefits of sheltering woods in cold bleak situations. Dr. 

 Brown of Lanfine, in an essay lately published on some fossil 

 trees found on his estates, gives it as his opinion, that the climate 

 must once have been many degrees warmer ; the cause of the 

 cold he attributes to the removal of the woods once existing. A 

 great quantity of sensible (not latent) heat must have been 

 retained by the vast amount of confined air (which is the best 

 retainer of heat) generated in these woods; the electric conduc- 

 tors formed by the pointed trees would increase these effects ; 

 and the mass of heat thus stored up, to be given out slowly when 

 the air was colder than the wood, must have had a great effect 

 on the climate. 



Water from barren peat soils, Dr. Liebig says, yields much 

 humic acid ; and all agriculturists and gardeners agree, he adds, 

 that manure is not suitable for plants, till it loses the power of 

 giving colour to water. I have seen manure kept for years, 

 the drainings from which were as brown as ever. I never heard 

 the remark made, and imagine the manure would produce little 

 effect if so far decayed. I think, however, there is some 

 mistake about the benefits derived from humic acid; it abounds 

 in moss water, as before quoted from Dr. Thomson, and above 

 from Dr. Liebig ; and, from a substance so plentiful, it is won- 

 derful we have not heard of its great effects, accidentally, from 

 practice : perhaps the antiseptic principle of tannin, also con- 

 tained in the moss water, may help to prevent the small quantity 

 1 part in 2,500 from taking effect ; if it were mixed with quick- 

 lime, humate of lime, said to be a more soluble substance, 

 might be formed. Dr. Liebig says the humate of lime is not 

 more soluble than humic acid. Whatever may be the fate of 

 the theory of humic acid, it is, I believe, almost wholly allowed 

 by gardeners, that manure yielding this brown-coloured water 

 is in the fittest condition for plants : they are constantly in the 

 practice of watering with the brown-coloured water, and of ex- 

 tolling its effects. In Holland they are said to wash the dung, 



I 4 



