The student will, no doubt, at once perceive that if we concentrate the light of the sun upon an object, we shall also concentrate the heat, and either melt or consume it. A screen is therefore used in such cases, which will allow the light to pass while holding back the rays of heat. A solution of alum is found to answer the purpose admirably. ------------------------------------------------------------------------ CHAPTER IX. THE TELESCOPES OF GALILEO, GREGORY, NEWTON, HERSCHEL, LORD ROSSE, AND FOUCAULT. IF history has failed to furnish us with the name of the inventor of the microscope, we have very exact information as to the first experimenters upon the powers of the telescope. “In the archives of the Hague,” says Arago, “we find documents, by the aid of which Van Swieten and Moll have come to a decisive conclusion as to the first and true inventor of the telescope.” We read in these documents that a spectacle-maker of Middleburg, named John Lippershey, addressed a petition to the States-General on October 2, 1606, in which he asked leave to take out a patent, which should constitute him the only maker of this instrument, or which should confer upon him an annual pension, on the condition of not manufacturing them for other nations. The petition qualifies the instrument as serving to see distinct objects, as had already been explained to the members of the States-General. On the 4th of October, 1608, the States-General appointed a deputy from each province to experiment on the new instrument, which was placed on a tower of the palace belonging to the Stadtholder. Huggard says that the first telescopes experimented on were a foot and a half in length. On the 6th of October, the commission declared the instrument of Lippershey to be useful to the nation, but demanded that it should be made for two eyes instead of one. On the 9th of December, Lippershey, having announced that he had solved the problem, Van Dorth, Magnus, and Van der Au were ordered to verify the fact, which they did by making a very favourable report on the 11th of the same month. The binocular instrument was therefore found to answer.