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302  metallic wires or cables to a great distance with but little loss, comparatively speaking, and could thus be made to run magneto-electric engines to do the work of steam in our mills and workshops, to ignite electric lamps, etc. A copper rod, or cable, three inches in diameter, says Dr. Siemens, would be capable of transmitting a thousand horse-power to a distance of say thirty miles—an amount sufficient to give the light of a quarter million of candles, and suffice to illuminate a town of moderate size. Two eminent American investigators, Professors Houston and Thomson, of Philadelphia, having just made an investigation with the especial purpose of determining the practicability of transmitting the power of Niagara to great distances by means of electricity, go even further than Dr. Siemens. They make the astonishing assertion—and, what is more, they prove it—that it would be possible, should it prove to be desirable, to convey the whole power of Niagara to the distance of 500 miles or more by means of a copper cable not exceeding a half inch in thickness.

It is unnecessary for me to multiply examples upon this fruitful theme of speculation, for the time admonishes me that I have already trespassed sufficiently upon your attention, and I think I have convinced you very fully that such queries as What shall we do when our coal-fields are exhausted? need cause us no anxiety, for centuries before this possibility shall be realized, I opine, the world will no longer stand in need of them.



HE geological survey of the country bordering the fortieth parallel of latitude was made under the direction of the War Department by a party under Mr. Clarence King, who took the field in 1867. The area covered by the survey was a belt one hundred miles wide, traversed by the Pacific Railroad between the Great Plains on the east and the Sierra Nevada on the west, approximately between the 104th and 120th meridians of longitude. The general object of the survey was to connect the region of which the geological structure has been made known through the California survey on the west with the explored portion of the Mississippi Valley, and thus to supply the material for completing a section across the continent. In addition to this it was proposed to determine by careful investigation the structure and resources of the country lying adjacent to the Pacific Railroad, which by the construction of this great work was opened to occupation, and was already invaded by a population eager to seize and develop its hidden stores of mineral wealth.