. The art of projecting. A manual of experimentation in physics, chemistry, and natural history, with the porte lumière and magic lantern. , and the othertwelve inches. Let the tines be two inches apart, andthe flat sides should face each other on each fork. Astem may be now welded upon the bend ; it should beabout five-eighths of an inch in diameter, three or fourinches long, and made of round steel. When one ofthese forks is struck in the manner of common tuning-forks, it will be seen to vibrate through quite a largearc, and will continue to vibrate perceptibly to the eye,for half a minute o
. The art of projecting. A manual of experimentation in physics, chemistry, and natural history, with the porte lumière and magic lantern. , and the othertwelve inches. Let the tines be two inches apart, andthe flat sides should face each other on each fork. Astem may be now welded upon the bend ; it should beabout five-eighths of an inch in diameter, three or fourinches long, and made of round steel. When one ofthese forks is struck in the manner of common tuning-forks, it will be seen to vibrate through quite a largearc, and will continue to vibrate perceptibly to the eye,for half a minute or more. If, while the fork is vibratingthe stem be held upon a table or floor, or some otherresonator, a deep sound will be heard, and the largerone will make about fifty vibrations per second, whilethe shorter one will probably make seventy or seventy-five vibrations per second. A stand will be needed foreach of these, and may be made by mortising a postthree inches square, and three or four inches high, intoa board eighteen inches long and ten inches wide(Fig. 43). This post should have an inch-and-a-half 68 THE ART OF hole bored throughit lengthwise, s othat a smooth stemmay freely turn init. This stemmust have a largehead upon it, thro which is bored a -^*^* ^^ hole to receive the stem of the fork. Set-screws should be provided, tofasten the stems in their proper places. These sup-ports might be made of cast-iron, in which case theywould not need to be nearly so large. Next make four slides of iron, an inch and a half ortwo inches long, and bent so as toslide upon the fork and be fixed witha set-screw where it is are for loading the forks andmaking them vibrate slower, as theyare nearer the ends. Lastly, each fork will need a smallmirror fastened to its end. TheTig. 44. small, round pocket mirrors, about an inch in diameter, I have found to answer well ; butcare should be taken, in selecting these glasses, to getplain mirrors. Most of these small
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherbosto, bookyear1877
