Word: disks
(lookup in dictionary)
(lookup stats)
Dates: during 1885-1885
Sort By: most recent first
(reverse)
...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 exactly corresponding to the desired convexity of the lens, thus, in reality forming a species of mould. This disk, which by the way is called the "tool," is placed on the glass, and by a simple mechanical device is made to rotate upon it. When the grinding is completed...
...which reduced the great number of contestants. The Greeks never leaped without weights, and used two sorts, first the dumbbell, which had a curved bar between the round ends, and of which the dumbbell in use at the present day is an imitation; second, the half of a flattened disk, with an orifice on the curved side for the hand; these they threw behind them when in mid-air, and this gave them additional impetus. By the aid of these weights tremendous distances were covered; for instance, Herodotus tells a little story of a certain Greek who had a record...
...Washington telescope, which, at that time, had just been completed. To build a telescope of such dimensions was a tremendous undertaking. Agents travelled through Europe visiting the most noted firms in England, France and Germany, without finding one which was willing to undertake the contract of making the glass disks from which the objectives must be made. At last, in 1880, a contract was made with Feil of Paris, for an objective of 36 inches clear aperture. For four years he has worked without success, every disk breaking on account of the heat which is necessary in the last stage...