In the year 1844 electricity, last and mightiest of the servants of man, was seized and harnessed and made to do practical work. A telegraph line was erected between Washington and Baltimore. [Footnote: See _Invention of the Telegraph_.] In 1846 mathematics achieved perhaps the greatest triumph of abstract science. It pointed out where in the heavens there should be a planet, never before known by man. Strong telescopes were directed to the spot and the planet was discovered. [Footnote: See _The Discovery of Neptune_.] Man had found guides more subtle and more accurate than his own five ancient senses. The age of figures, the age of electricity, began. The changes were symbolic, perhaps, of the more rapid rate at which the forces of society were soon to move. Over all Europe and America great events were shaping themselves with lightning speed. Tremendous changes political and economic, social and scientific, were hurrying to an issue. THE MEXICAN WAR In America the Mexican War, vast in its territorial results, still more so in its effect upon society, broke out in 1846 over the admission of Texas to the United States. The superior fighting strength of the more northern race was at once made evident. Small bodies of United States troops repeatedly defeated far larger numbers of the Mexican militia. The entire northern half of Mexico was soon occupied by the enemy. Expeditions, half of conquest, half of exploration, seized New Mexico, California, and all the vast region which now composes the southwestern quarter of the United States. [Footnote: See _The Acquisition of California_.] Farther south, however, the more populous region wherein lay the chief Mexican cities remained resolute in its defiance; and the Washington Government despatched against it that truly marvellous expedition under General Scott. The heroisms and the triumphs of Scott's spectacular campaign deserve to be sung in epic form. The dubious justice of the war was forgotten in its overwhelming success. From the captured Mexican capital the conquerors dictated such peace terms as added to the United States almost half the territory of her helpless neighbor. Europe at last awoke to the fact that there was but one Power on the American continent, a power with which even the mightiest monarch could ill afford to quarrel. [Footnote: See _The Mexican War_.] The very year in which the final treaty of peace was signed (1848) the Mormons, a religious sect, finding themselves unwelcome and out of place in Illinois, moved westward in a body. Enduring every hardship, every privation, perishing by hundreds in the trackless deserts, captured and put to torture by the Indians, they still persevered in their migration, and, halting at last in the valleys of Utah, began the settlement of the Central West. [Footnote: See _Migrations of the Mormons_.]