Thomé de Gamond was to turn into an incomparably zealous and persistent projector of ways in which people could cross between England and France without getting wet or seasick; he devoted himself to the problem for no less than thirty-four years, and had no hesitation in exposing himself to extraordinary physical dangers in the course of his researches. Unlike the plans of his predecessors, Thomé de Gamond's were based upon fairly systematic hydrographic or geological surveys of the Channel area. In 1833 he made the first of these surveys by taking marine soundings to establish a profile of the sea bottom in a line between Calais and Dover; on the basis of this, he drew up, in 1834, a plan for a submerged iron tube that was to be laid down in prefabricated sections on the bed of the Strait of Dover and then lined with masonry, the irregular bottom of the sea meanwhile having been prepared to receive the tube through the leveling action of a great battering-ram and rake operated from the surface by boat. By 1835, Thomé de Gamond modified this scheme by eliminating the prefabricated tube in favor of a movable hydrographic shield that would slowly advance across the Channel bottom, leaving a masonry tube behind it as it progressed. But the rate of progress, he calculated, would be slow; the work was to take thirty years to complete, or fifteen years if work began on two shores simultaneously. Thomé de Gamond moved on to schemes for other ways of crossing the Channel, and between 1835 and 1836 he turned out, successively, detailed plans for five types of cross-Channel bridges. They included a granite-and-steel bridge of colossal proportions, and with arches "higher than the cupola of St. Paul's, London," which was to be built between Ness Corner Point and Calais; a flat-bottomed steam-driven concrete-and-stone ferryboat, of such size as to constitute "a true floating island," which would travel between two great piers each jutting out five miles into the Channel between Ness Corner Point and Cap Blanc-Nez; and a massive artificial isthmus of stone, which would stretch from Cap Gris-Nez to Dover and block the neck of the English Channel except for three transverse cuttings spanned by movable bridges, which Thomé de Gamond allowed across his work for the passage of ships. Thomé de Gamond was particularly fond of his isthmus scheme. He traveled to London and there promoted it vigorously among interested Englishmen during the Universal Exhibition of 1851, but he reluctantly abandoned it because of objections to its high estimated cost of £33,600,000 and to what he described as "the obstinate resistance of mariners, who objected to their being obliged to ply their ships through the narrow channels."