LECTURES AND ESSAYS. 397 



The water line at Grayling is about 15 feet below the surface. If we 

 can draw upon this sub-soil supply of water for our crops we may do much 

 to mitigate the drought and promote growth. Our hold upon this water is 

 by means of the capillary power of the soil. The means by which we may 

 modify the capillary power of the soil deserves attention. A lamp wick 

 which draws up oil, to feed the flame, by capillary action, must not be too 

 tight or too loose in the socket to act satisfactorily. Capillary action in the 

 soil has similar limitations, and a certain porosity in the soil will secure the 

 best capillary action. By compressing a loose and porous soil we increase 

 its capillary power. This is one great benefit from the use of the roller on 

 these soils. This increase of capillary action by the use of the roller is not 

 the only advantage on these sands. A compact seed bed is a necessary con- 

 dition for vegetable growth. If anyone will examine the wagon roads run- 

 ning through these plains — the old, wandering cross-lots roads through the 

 woods — and will observe the heavy sward of grass where the soil has been 

 beaten down and compressed by the passing wheels and the feet of the teams, 

 he will see evidence of the benefit of compacting this soil. The roller will 

 do as much for these lands as the plow. But the roller needs to be a heavy 

 one to give the best results. I made a mistake in getting too light a roller. 



In many soils loss of water by evaporation is checked by keeping the sur- 

 face so thoroughly stirred as to prevent surface capillary action, and thus a 

 non-conducting surface is interposed between the drying air and the moist 

 soil beneath, and in this way the loss of soil-water by evaporation is dimin- 

 ished. "Proper cultivation is irrigation," says Dr. Sturtevant. To a 

 limited degree this is true of most soils. Is it true of these sands? Light 

 cultivation of hoed crops will mitigate drought ; what will be the effect of 

 lightly harrowing meadows and sown crops at the beginning of a drought, 

 and at intervals during its continuance? 



The relation of these sands to capillary water, surface evaporation, etc., 

 will be made a special study the coming season. 



a. Plowed. ] 1st. Surface soil, 



b. Plowed and harrowed. 1 to 8 inches. 



c. Rolled. } 



d. Sodded. | 2d. Subsoil, 



e. Lightly stirred or raked after rolling. J 8 to 16 inches. 



MANURES EMPLOYED. 



Let me call your attention to the manures used on these lands. 



Marl is found in large quantities in swamps and small lakes in these 

 northern counties, and the first cost of the material is nothing. The only 

 question is the expense of removal from the marl beds, and of spreading it 

 on the land. The benefit of marling is immediate and lasting, and there is 

 little danger of injury from its free application. 



The good effects of applying marl on the expermental fields were evident. 

 On the south field the marl was placed in a large pile before the land was 

 ready for marling, and when it was removed to dress the field, a heavy marl- 

 ing was left where the marl heap was placed. Here a heavy growth of grass 

 was found making an island of green, visible at some distance. 



The small lake on the school section, near the experimental farm, contains 

 thousands of tons of marl. It has the following composition : 



