Scientific amusements . ment is based uponthe property possessed by a convex lens or concave mirror,?of converging to a focus the rays of light falling on it•from any object, and at that point or focus forming animage of the object. The following diagram will illustratethis. Let vw be a lens, and AB an object between theglass, and F the focus. The ray, he, is so refracted asto appear to come from a. The ray from b likewiseappears in a similar way, and a magnified image, ab, isthe result. I20 OPTICAL APPARATUS. The ordinary Telescope consists of an object-glass andan eye-lens, with two intermed
Scientific amusements . ment is based uponthe property possessed by a convex lens or concave mirror,?of converging to a focus the rays of light falling on it•from any object, and at that point or focus forming animage of the object. The following diagram will illustratethis. Let vw be a lens, and AB an object between theglass, and F the focus. The ray, he, is so refracted asto appear to come from a. The ray from b likewiseappears in a similar way, and a magnified image, ab, isthe result. I20 OPTICAL APPARATUS. The ordinary Telescope consists of an object-glass andan eye-lens, with two intermediates to bring the objectinto an erect position. A lens brings it near to us, anda magnifier enlarges it for inspection. We will now givea short history of the Telescope and its, improved con-struction. Roger Bacon was supposed to have had some knowledgeof the Telescope, for in 15 5 i it was written : Greattalke there is of a glass he made at Oxford, in which mensee things that were don. But a little later, Baptista. Converging rays to a focus. Porta found out the power of the convex lens to bringobjects nearer. It was, however, according to the oldtale, quite by an accident that the Telescope was discoveredabout the year 1608. In Middleburg, in Holland, lived a spectacle-makernamed Zachary Jansen, and his sons, when playing withthe lenses in the shop, happened to fix two of them atthe proper distance, and then to look through both. Tothe astonishment of the boys, they perceived an invertedimage of the church weathercock much nearer and muchlarger than usual. They at once told their father whatthey had seen. He fixed the glasses in a tube, and THE TELESCOPE. 121 having satisfied himself that his sons were correct, thoughthttle more about the matter. This is the story as told,but there is little doubt that for the first Telescope theworld was indebted either to Hans Lippersheim or JosephAdriansz, the former a spectacle-maker of Middleburg ;and in October 1608, Lippersheim pres
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Keywords: ., bookcentury1800, bookdecade189, booksubjectscientificrecreations
