Page:Popular Science Monthly Volume 88.djvu/557

 Popular Science Monthly

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��Fun With Pictures of Your Friends

IF you would like to have a little fun with your friends, try enlarging a group negative or single figure after this fashion : First place the negative in the enlarging frame in the usual manner. After the desired size of print has l)een decided upon and focus made for size, tip the frame or sliding-board (on which sensitized paper is placed) gradually backward, until the persons or scenes assume fantastic shapes. The best angle of the board will probably be around forty-five degrees, although some nega- tives require a greater angle to change them.

A print from the negative of your thin friend will reveal him as a very stout person, but without losing the facial like- ness in the process. By tipping the board backward, everything seen in the

���Diagram showing the arrangement of the sliding - board for making trick pictures

negative, is lengthened, so that the fat man becomes a tall, thin person and a stubby tower becomes a factory chimney. The length of exposure needed will be found to be about the same as when the board is in the normal position. Dura- tion of exposure depends on the size of the stop used. It is not necessary to

��own an expensive enlarging outfit, since the trick can be done on anything from a "Brownie" to the professional appa- ratus. Try it on your friends.

����Tip your sliding-board at forty-five degrees

sidewise and you make the whole world rotund

and happy

��If the tilt of the board is the length of

the picture, thinness becomes an

attribute of all

A Metal- Vapor Light That Is White

ANE^^' vapor lamp employing the vapor from metals has been patented by a German scientist. Zinc chloride and zinc bromide have been used and give the best results at at- mospheric pressure. As in the mercury- \apor arc, the inclusion of air or other foreign gases in the tube is prejudicial. On the other hand, an arc in an atmosphere of aluminium chloride or titanium chloride is more stable, and an admixture of nitrogen is harm- less. Oxygen, however, must be excluded. It is stated that the color of the light is white, and that the efficiency is in the neigh- l)orhood of that of the mercury- vapor lamp.

The fact that the light is white will greatly add to the importance of the lamp, since there are many uses which demand such illumina- tion.

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