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16 and multiplying population, and its influence on the minds and bodies of such population; together with the conceivable uses of machinery on a colossal scale in accomplishing mighty and useful works, hitherto unthought of, such as the deepening of large river channels;—changing the surface of mountainous districts;—irrigating tracts of desert in the torrid zone;—breaking up, and thus rendering capable of quicker fusion, edges of ice in the northern and southern Arctic seas, etc., so rendering parts of the earth habitable which hitherto have been lifeless, are to be studied under this head.

The value of instruments is, secondarily, in their aid to abstract sciences. The degree in which the multiplication of such instruments should be encouraged, so as to make them, if large, easy of access to numbers (as costly telescopes), or so cheap as that they might, in a serviceable form, become a common part of the furniture of households, is to be considered under this head.