Word: lensed
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A recent visit to the workshop of the famous lens makers, Alvin Clark & Sons, Cambridgeport, furnishes some interesting facts concerning the objective for the great telescope of the Lick Observatory in California. It being impossible to get the glasses cast satisfactorily in this country, the Clarks sent to Paris after...
The grinding and the polishing are done as follows: In the first place the curves of the lens are determined by experiments with smaller models, aided, of course, by the maker's long experience. Then an iron disk, large enough to-cover the glass, is made into a concave shape...
When the two glasses are finally set in the brass mountings and the lens is complete, the diameter of clear glass inside the fittings will be three feet, the lens having a focal distance of 57 feet! This means that the cylinder of the telescope itself will be at least...
The beginning of the microscope of to-day is traceable to the small, single lens instrument of the sixteenth century, called at the time Vita pulicaria, or flea-glass, because by its aid the true beauty of the flea, in outline and detail, was first brought clearly before the public...
In this country and in England the objectives and oculars are named in inches or fractions of an inch, relatively to the focal length of a simple lens which will produce the same magnification. Thus taking the focal length of the eye as ten inches, a one inch objective magnifies...