'STONE ON A FARM. 213 



times great rocks as well, by the force of their im- 

 petuous currents. And, as a very large, if not the 

 larger portion of our earth's surface bears testimony 

 to the existence and powerful action through ages, of 

 larger and smaller water-courses, a wide and general 

 diffusion of stones, not in place, but more or less trit- 

 urated, smoothed, and rounded, by the action of 

 water, was among the inevitable results. 



These stones are sometimes a facility, but oftener 

 an impediment, to efficiency in agriculture. "When 

 heated by fervid sunshine throughout the day, they 

 retain a portion of that heat through a, part of the 

 succeeding night, thereby raising the temperature of 

 the soil, and increasing the deposit of dew on the 

 plants there growing. When generally broken .so 

 finely as to offer no impediment to cultivation, they 

 not merely absorb heat by day, to be given off by 

 night, but, by rendering the soil open and porous, 

 secure a much more extensive diffusion of air through 

 it than would otherwise be possible. Thus do slaty 

 soils achieve and maintain a warmth unique in their 

 respective latitudes, so as to ripen grapes further 

 North, and at higher elevations, than would other- 

 wise be possible. 



The great Prairies of the West, with a consider- 

 able portion of the valleys and plains of the Atlantic 

 slope, expose no rock at their surfaces, and little be- 

 neath them, until the soil has been traversed, and 

 the vicinity of the underlying rock in place fairly at- 

 tained. To farmers inured to the perpetual stone- 



