36 



pleasant and moist than inland regions less favourably situated, are at the same time 

 elevated in temperature by passing over the heated land, thus being enabled to retain the 

 moisture which, passing over a cooler surface, they would precipitate. This condition of 

 the air continuing throughout the whole summer season, the natural consequence would 

 be that the summer would be drier than where the surface is protected by trees. With a 

 bare, treeless surface, therefore, there would be : — 1. An autumn warm and moist. 2. A 

 winter with much snow, falling irregularly and much cold wind from the north and north- 

 west. 3. A spring raw and cold, with prevailing north-west winds, with necessarily a 

 large precipitation of moisture. 4. A hot and comparatively dry summer. 



" Interposing among these phenomena the influence of trees, the relative rate of cooling 

 between the water and the land greatly changes. With the sun's rays beating down on the 

 ground it will frequently rise to ninety or ninety-five degrees; but a tree intercepting the 

 sun's rays prevents the high temperature of the ground. Now, though the intercepting tree 

 does become elevated, the rise is slower and never reaches the same height as that of the 

 bare soil for several reasons : — 1. The green foilage is not so good an absorbent of heat 

 as, say a dark soil. 2. Since the tissues of the trees are full of sap, and since the specific 

 heat of water is about four times as great as that of the soil, the sap will not rise in 

 temperature so rapidly as would the soil. 3. On account of the circulation of the sap, 

 successive portions are being continually presented to the heating influences of the sun's 

 rays, but as the rapidity of circulation is increased with heat, and as the sap, coming up 

 from the deep portions of the earth surrounding the roots, must have a comparatively 

 low temperature, the elevation in temperature of the whole volume of sap must 

 necessarily be slow. 4. The much greater amount of evaporation taking place from the 

 leaves and branches of the tree than does from the soil, produces a greater degree of cold 

 than would be produced by less evaporation. 5. The greater amounts of moisture in the 

 air surrounding trees will prevent a rapid rise in temperature. These causes combined 

 prevent the tree from attaining to the maximum temperature till evening. Radiation 

 from its surface then setting in will be much slower than in the case of the soil. Hence 

 the temperature does not sink so low as that of the unprotected soU. 



" He proceeded to explain the efiect over a whole country clothed with forests, con- 

 tending that while the slower decrease of the trees temperature in autumn augured a 

 higher temperature, the moderating influences of forests on the winter were beyond 

 question. ■ In spring, the sun's rays being intercepted cannot melt the snow so rapidly, 

 and on this account spring floods are largely prevented, the winter grains and clover are 

 protected for a longer period from the effects of thaws by day and frosts by night. 

 Slower radiation prevents so many night thaws, and the baneful chilling influences of cold 

 raw winds are much mitigated. Among other things, the trees, becoming elevated in 

 temperature but slowly, act as condensers to the vapours swept over them from the 

 surface of the lakes, thus supplying frequent showers to the growing plants, while at the 

 same time, by preventing so rapid evaporation, they aid the rains in efiecting their fructi- 

 fying influences. 



"The reader then proceeded to consider at length Canada's present condition, and in 

 doing so remarked that where settlement has existed for at least twenty-five years, three- 

 quarters of the forest has been destroyed, while in few cases is the preserved wood dis- 

 tributed over the surface with any regard to its protecting influences, so it may be said, 

 that three-fourths of the influences that would be exerted in our climate under a treeless 

 surface are at work. 1. A cold, raw s{)ring, with high winds and frequently much dry 

 weather during germination. 2. A hot summer, with but little rain, the dryness increas- 

 ing regularly from May to August. 3. An irregular winter, with frequent high winds, 

 irregular snow falls, etc. These conclusions would be borne out by the following 

 statistics : — 



The total precipitation of moisture has decreased. Thus the 



Total Snow and Rain. 



1840-44 216.57 inches. 



1850-54 164.684 „ 



1860-64 160.387 „ 



1870-74 152.62 



