1261. Why is silica diffused over the stems of wheat, grasses, canes, &c.?
Because it affords strength, density, and durability, to structures that are very light, and which, but for this beautiful provision, would be exceedingly perishable.
"For in this mountain shall the hand of the Lord rest, and Moab shall be trodden down under him, even as straw is trodden down for the dunghill."—Isaiah xxv.
1262. Why is guano a productive manure?
Because it contains, with other suitable elements, an abundance of the silicous skeletons of animalculæ.
1263. Why does a wheat-crop greatly exhaust the soil?
Because, as well as the carbon, and the salts, which form the straw and the grain, it draws off from the soil a great amount of silica.