WATER CONDUCTIVITY OF SOILS. 

 Of tlie total rainfall was filtered — 



151 



By soil covered with moss 



By soil naked 



By soil covered with hecch growtli 

 By soil covered with spruce growth 



1886. 



Per cent. 

 7 



5.1 

 4.1 

 3 



1887. 



Per cent. 

 C. 2 

 3.5 

 2.9 

 1.5 



In regard to the amount of filtration which various soil-cover.s allow, 

 we have the following- very instructive results from the experiments of 

 Wollny, in which the amounts of rain and corresponding filtration on 

 62 square inches sui face are given : 



May to September, 

 1886 — total rain 

 28,529 grams. 



Amount, 

 grams. 



Oak leaves : 



5 centimeters . 

 10 centimeters , 

 20 centimeters 

 30 centimeters 



Spruce litter; 



5 centimeters , 

 10 centimeters 

 20 centimeters 

 30 centimeters 



Pine needles : 



30 centimeters 



Moss: 



5 centimeters 



Bare soil: 



30 centimeters 



17, 591 

 19, 482 

 21. 160 

 21, 061 



17, 793 

 19, 277 

 19, 523 

 19, 467 



19, 734 



14, 993 



11,610 



Per cent 

 of rain- 

 fall. 



61.7 

 68.3 

 74.1 



73.8 



62.4 



67. 5 



68. 3 

 68.2 



69.2 



52.5 



40.7 



April to September, 

 1887— total rainfaU 

 18,652 grama. 



Amount, 

 grams. 



Per cent 

 of rain- 

 fall. 



7,894 



7,353 



12, 954 



13, 272 



8,653 



7,356 



14,611 



13,912 



9,784 



7,260 



3,636 



42.3 

 39.4 

 69.4 

 71.2 



46.4 



39.4 

 78.3 

 74.6 



52.4 



38.9 



19.5 



These figures show that a litter will filter considerably larger amounts 

 of water than a soaked soil of the same depth, and that the moss cover 

 allows less Avater to filter than the litter. This is accounted for by the 

 soil needing a larger amount of water to supply thB moisture evapo- 

 rated than the litter which remains moist. 



Notable is the influence which the thickness of the cover exerts upon 

 the amounts of drain water and also the relation of the amount of pre- 

 cipitation to the amount of filtration. 



It will be noticed that with a thicker cover to 1 foot in depth (30 

 centimeters) the amount of precipitation hardly changes the amount of 

 drain water, while the lighter covers have mucli less power to preserve 

 a small precipitation, for of course the amounts not drained are evapo- 

 rated. 



E. Ebermayer (Sickerwassermengen in verschiedenen Bodenarten 

 Wollny 1890) from a long series of experiments comes to the conclusion 

 that besides clay, it is especially humus, which imbibes almost all pre- 

 cipitation and gives up very little water below. 



A layer of garden mold of 1 m. furnished only 3.2, 5.7, and 7.1 per 



