20 FORESTRY BULLETIN 



take up water most readily, retain it in least quantity and part with it 

 most rapidly by evaporation. One hundred parts of pure sand will 

 take up 25 parts of water, and will lose 22 parts by evaporation in four 

 hours when spread out in a thin sheet in dry air. Such soil is well called 

 leachy and very subject to drought. 



If to such sand, clay, oxide of iron and marl, carbonate of lime, are 

 added, the power of such mixed soil to retain water is much improved, 

 but the material that has the greatest influence, and the one most within 

 our control is humus or the organic matter of soil. An experiment showed 

 this clearly. A glass funnel was used holding a very small filter paper in 

 its throat (and thoroughly wet) to prevent the sand flowing through. Into 

 this funnel 100 grains of dry sandy soil from Grayling were placed, and 

 water poured over the sand till completely wet, and the excess of water 

 drained off till dripping had ceased. This soil contained 95 per cent, of 

 sand and 2^ per cent humus. It took up and retained by capillary attrac- 

 tion 29 per cent, of water. Left undisturbed for 3 days in the shade it 

 lost 27.7 parts of water, retaining only 1.3 parts out of the 29. 



A soil was prepared by mixing two parts of Grayling sand with one 

 part of Kalamazoo muck (containing 63.76 per cent, of humus). The ma- 

 terials were thoroughly mixed and sifted and 100 grains of the mixed soils 

 were placed in a glass funnel the same as in former experiment, and water 

 poured over it till saturated, when it was found that 100 parts of this soil 

 took up and retained 65 parts of water. On leaving it exposed for 3 days 

 in the same way, the soil lost 45 parts of water, but still retained 20 parts 

 of the original 65. In other words, the addition of 21 per cent, of humus 

 to a sand containing 2J per cent of organic matter, more than doubled 

 its capacity to take up water by capillarity, and increased by more than 

 15 fold its power to resist evaporation. 



A similar set of experiments, using jelly cups in place of funnels, gave 

 concordant results. It is thus shown that the beneficial influenee of the 

 organic matter of the soil in mitigating drought in sandy soils is twofold: 

 assisting such soil to take up and hold the rain when it falls, and prevent- 

 ing excessive loss by evaporation. 



The damage by forest fires sweeping over the country, burning up leaves 

 and grasses which would form humus, and consuming much of the humus 

 already in the soil, becomes evident to all. These forest fires inflict in- 

 calculable injury upon our northern plains. The thwarting of Nature's 

 efforts at reforesting, by burning up all trees and shrubs too young to 

 resist the fire, is clearly seen as one travels over the blackened country. 



Keep out the fires is the first and great commandment in forestry for 

 Michigan. Without this no effort at reforesting will accomplish much. 



METEOROLOGICAL OBSEKVATIONS FOE THIRTY FOUR YEARS AT THE MICH- 

 IGAN AGEICDLTUBAL COLLEGE. 



To satisfactorily study these questions of the relation of climate to 

 forestry, we need a long series of observations taken at leading points in 

 the State. Unfortunately these are wanting, but as a contribution to this 

 end the following mean monthly observations at the Agricultural College 

 are presented. They are too local to be decisive of the average climatic 

 condition of our State, but may yet be of some value in future studies 



