To avoid expensive waste of paper in making large bromide enlargements the following device is useful: Cut an oblong sheet of stiff cardboard, 5¹⁄₄ by 4 in., with a central opening, measuring 3³⁄₄ by 1¹⁄₂ in. Along the lower edge of the central opening mark off five spaces of ³⁄₄ in. each, and number them from 1 to 5. Glue a strip of cardboard, 1 in. wide, at the top and the bottom of the oblong, on the back. Now glue a second strip of cardboard over each of those just attached, making the second strips slightly wider to form grooves similar to those in a sliding-top box.
Cut a piece of cardboard, wide enough to slide easily in these grooves, and about 7 in. long. In the center of it, cut an opening, 1¹⁄₂ in. long and ³⁄₄ in. wide, with the longer dimension extending across the strip. By inserting this slide into the grooves, the opening in it may be shifted to correspond to any of the five ³⁄₄-in. indications at the lower edge of the opening in the oblong frame.
Focus the enlargement on the easel and put the cap on the lens. Then pin a 1¹⁄₂-in. strip of bromide paper where a good range of detail will fall upon it. Pin the oblong card over the bromide strip and make five successive exposures, of increasing duration, by sliding the strip so that its opening is opposite the number indications on the oblong. Note the particulars of exposure at the time and later develop the strip of bromide paper. Suppose the exposures were of 8, 16, 24, 32, and 40 seconds’ duration, and upon development it was found that the first and second exposures were much underexposed and that the fifth was overexposed; the third and fourth being only slightly under and overexposed, respectively. Then the mean of these two, that is 24 plus 32 divided by 2, or 28 seconds, will be approximately the correct exposure. The use of this device will effect a considerable saving.—H. J. Gray, Lewes, Sussex, England.
Scale on Vaulting Pole Indicates Points of Grip
Indications on the Vaulting Pole Aid the Athlete in Finding the Proper Grip
Unnecessary delay in running off the pole-vaulting events at athletic meets is caused by the repeated testing of vaulters for the proper height at which to grip the vaulting pole. This was readily overcome by marking intervals of 1 ft. on the upper end of the vaulting poles. Vaulters judge the proper height once and thereafter may easily take the same grip with the aid of the indications on the pole.—A. B. Wegener, Madison, N. J.
Current of Canal Raises Irrigation Water
The Current of the Canal Causes the Wheel to Revolve, Carrying the Water to the Trough