LANTERN SLIDES, Method of Making. Lantern slides are so universally used in edu cational work and are so easily• made that teachers should know the process. Besides, lanterns, which can be attached to any electric , light socket, have become so cheap and so efficient that illustrated descriptions of travels and outings may be enjoyed in the home. As far as the method of making them is con cerned, there are three classes of lantern slides : (1) lantern slides by contact, (2) by reducing or enlarging, and (3) by copying illustrations or photographs.
1. Lantern Slides by Contact.— Put the lantern slide plate on the negative in a print ing frame and print just as if the plate were a piece of printing-out paper. The tithe of ex posure will be rather short. With a gas man tle lamp or an• ordinary electric-light bulb, try two seconds at a distance of three feet. If the negative is weak, increase the distance, underexpose and develop thoroughly; if the negative is dense, lengthen the exposure. If the negative is uneven, increase the distance so that 8 or 10 seconds, or even longer will be required for the exposure. This will give an opportunity for shading the weaker parts, just as in printing on paper. With most kodak films and with other negative's up to 34)(4% inches, this is the best method. Even with larger negatives, a desirable print may be covered by the plate and a print made of that particular feature.
2. Reducing and If a lantern slide is to be made from a negative either smaller or larger than the lantern slide plate, a camera is. necessary. Place the negative in
a perfectly vertical position so that a good light, but not direct sunlight, may shine through it, as in making an ordinary picture. Remember that the lantern slide plate is very slow, so that the exposure will be 10 to 15 times that required for plates or for kodak films. Lantern slides made by reduc tion from larger negatives are likely to be the best•, enlargements from negatives smaller than the lantern slide are not so satisfactory.
3. Copying Illustrations or Photographs. In making lantern slides from photographs, maps or pictures in books, it is necessary to make a negative and then make a lantern slide from the negative. Preferably, this negative should be of the same size as the lantern slide plate. The lantern slide may then be printed by contact. Lantern slide plates may be used in making such negatives. If an average 5)(7 photograph is to be copied in good diffuse day light, with an F 16 stop, and a lantern slide plate, try an exposure of 15 seconds. In copying maps and line drawings, where dead blacks and pure whites are desired, expose .fully and overdevelop. Formulae for de velepors are furnished with every box of plates. Consult Chamberlain, Charles J., Meth ods in Plant Histology> (1901) ; The Photo miniature,) (Lantern Slides, Vol. I, No. 9, 1899).