Lynde, Carleton John, b. 1872, Gilbert, Alfred C. (Alfred Carlton), 1884-1961 · New Haven, Conn. : A.C. Gilbert Co. · leaf 60
No. 47. To make a Fig. 84. Why things are upside down \ GILBERT LIGHT EXPERIMENTS 57 … trench periscope. Get a block ofwood 4 X 4 X 6, measure down1 inch from each end and drawa line across diagonally. This linewill be at 45° to the length ofthe block. Cut the block throughon this diagonal line, see right sideFig. 85. Now attach a mirror to each diag-onal face by means of tacks. Cuta…
Light · Scientific recreations
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