8&4 ANNUAL REPORT, 
the average velocity of the wind be reduced to ten miles an hour. A : to ; 
the law of the radiation of heat, and the law above cited, two results AOS _ 
obtained: 
1st. By means of the reduced velocity of the winter winds, the shelter-belt area ie 
would show a relative increase of temperature due to the lessened radiation of 
heat from the soil, as compared with the treeless area. 
2d. There would be an absolute gain in the increase of the temperature i in the 
shelter-belt area, due to the friction of the air currents impinging upon the imnu- 
merable needle-like leaves of the trees composing the shelter-belts. 
What the precise difference in the winter temperature would be can ‘idle 
determined by a general series of observations extending over a considerable 
period of time. 
e 
Width and Compositton of Shelter-Belts. 
For the purpose of shelter, belts of one, two or three rows of evergreens will 
answer the purpose intended; but with a view to further profit the belts can be 
made seven or eight rods in width for the combined purpose of growing timber 
for farm use and market, and for shelter. In this form of planting cultivated 
forest, the evergreen can be grown at an enhanced profit, by a judicious admix- 
ture of larch, hickory, walnut and ash, etc., with the evergreens, and planting 
one row of Scotch pine or Norway spruce, or some other evergreen adapted to 
the soil and locality, upon each margin of the belts. By a series of systematic 
thinnings the hickory and the ash can be cut when they attain the size of hoop- 
poles, and these cuttings may be continued at subsequent periods for various 
uses, at a profit and -to the benefit of the evergreens; their wood being of but 
little value until they attain considerable age and size. 
The most valuable kinds of evergreen trees which have been tested and are 
known to be generally hardy or adapted to special soils and localities, and wor- 
thy of cultivation west of Lake Michigan, consist of the Scotch, Afstrian, Pitch, 
Mountain and White Pines, Norway and White Spruce, American Arbor vite and 
its hardy varieties, the Red Cedar and other species and varieties of the juniper 
family. 
Some of these species and varieties are of great value for both ornamental and 
economic uses. The species readily being propogated from seed, and the varie- 
ties from cuttings by the experienced planter 
Scotch and White Pines. 
The Scotch pine, although of European origin, seems to be at home in the 
north-west, making a rapid growth in all dry soils, even when planted in the 
most exposed situation, and subjected to drouth, and great extremes of tempera- * 
ture. The wood of this pine isstronger in every way, and the tree grows as rap- 
idly as the White pine, yet its wood is soft enough to be easily worked with ordi- 
nary carpenter tools, and the tree is subject to less percentage of loss in trans- 
planting and will prove more remunerative to the forest planter as a timber tree, 
and for the purpose of shelter, and should be largely planted in preference to the 
White pine, although the latter tree may be grown at a profit if carefully han- 
dled, and planted in proper soils and situations, or even in exposed situations, if 
protected by an admixture in the plantation of other kinds of trees. 
