In 1848 William went abroad and in England concluded a deal with William Henry Fox Talbot, British pioneer in photography, giving the Langenheims exclusive contract rights to the Talbot calotype process which used a negative from which any number of paper prints could be made. It was a vast improvement over the Daguerreotype negative-positive system which did not make possible printing of copies but the Langenheims were not successful in sub-licensing the Talbot process in America. Shortly after this the Langenheims made an important contribution to the art-science of light and shadow pictures by developing a system which made it possible to project the photographs in the old Kircher magic lantern. This prepared the way for the projection of a series of photographs showing a single movement. Kircher and the others who used his magic lantern, including the projection model of Uchatius, painted or drew their various scenes on glass slides. Until about 1850 when the Langenheim development was announced, there was no satisfactory method of making glass plates of positive photographs. Of course, the heat of the projecting lamp made it impossible to use pictures printed on paper. Frederic Langenheim, with U. S. patent No. 7,784, dated November 19, 1850, solved the problem. The Langenheim system was called “Hyalotype,” from the Greek, meaning “glass” and “to print” or to print on glass. Prior to the invention, some time in the winter of 1847–48, the period of the California Gold Rush, it was said the Langenheims, by means of a Viennese camera converted into a magic lantern equipped with a gas lamp, projected Daguerreotype pictures. This probably was achieved with the aid of a mirror system. The early Langenheim glass projector slides were circular and of a deep sepia tint; later excellent black-and-white plates were made. The Langenheim glass photo slides reproduced nature on the screen “with fidelity truly astonishing.” The two plates of the slide were made adherent with Canada Balsam, which is still used in this way as well as to attach parts of projection lens systems. Only very recently have new synthetic resins begun to displace Canada Balsam for these purposes. In 1851 the Langenheim Hyalotypes made their debut in Europe under great auspices, at the famous Exposition of the Works of All Nations at London. The glass projection photos were “very remarkable and well appreciated by competent visitors,” according to Robert Hunt, a pioneer British photographic authority, who inspected the exhibit and wrote about it. There is no evidence that the Langenheims combined their glass projection slides with the magic disk of Plateau to achieve motion pictures. They made one contribution and seemed to be satisfied with that. And it was successful for them, for in the next twenty-five years many thousands of these slides were sold in the United States.