During the |)eriod Colonel Davidson was in Cuba he reconstructed the entire length of the nearly wornout road, some one hundred and ten miles long, elevating it from a condition of almost complete uselessness to a first-class railway in all respects. The improvements introduced by him covered everything relating to permanent way, bridges, passenger, freight and water stations, as well as a complete revolution in equipment. He also constructed thirty-six miles of new and heavy line, reflecting great credit upon himself, especially for his wisdom and energy in completing in time some heavy rock-cutting and bridging, when a failure as to time would have been equal to loss of franchise to the company.

During his stay in Cuba he was often called upon to arbitrate delicate questions between conflicting interests, and his decisions were always looked upon as perfect and just solutions of the difficulties to be settled.

Shortly after Colonel Davidson's return from Cuba he was ap|)ointed chief engineer and superintendent of the Arizona Mining Company. He was in Arizona between two and three years in the exercise of these duties, and was at the same time United States Indian agent for the Territory.

In the years 18()5 and 1866 he was much occupied in the (]uestion of rapid transit for the city of New York, and was commissioned to proceed to London to observe and report upon the system of constructing and operating the underground railways in use there.

In 1867 he was named chief engineer of the New Haven and Derby Railroad, a short line involving many interesting points in location and construction, which be treated in the most successful manner.