Photomicrographs and Lantern Slides 141 



After a little practice the student will read with profit the more 

 extended works 011 this subject, among which are the following;: 

 The A, B, C of Photomicrography, by W. H. Walmsley (Tennant & 

 Ward, New York); Photomicrography, ed. by J. Spitta (Scientific 

 Press, London, England) ; Lehrbuch der Microphotographie, by 

 Dr. Richard Neuhaus (Harold Bruhn, Brunswick, Germany). 



LANTERN SLIDES 



Lantern slides are now so universally used in the lecture-room 

 that every teacher should be able to make them. Three general 

 classes of lantern slides, as far as the technic of making them is 

 concerned, will be described: (1) lantern slides by contact, (2) by 

 reducing or enlarging, and (3) by copying illustrations. 



1. Lantern Slides by Contact.- -This method is very simple. 

 Imagine that the lantern-slide plate is a piece of printing-out paper, 

 and proceed just as in making a print on paper. Remember that 

 dust on the negative or plate causes spots in the print, and that spots 

 so small as to be almost unnoticeable in an ordinary print will be 

 greatly magnified when they appear on the screen. Brush both 

 negative and plate very gently with a soft clean brush before making 

 the print. If the negative is 3|X4| inches, it can be placed in a 

 printing frame of that size, and the lantern slide placed upon it with 

 the two films in contact, just as in printing paper. If there is no 

 small printing frame, use a 4X5, a 5X7, or even an 8X10 frame. 

 In such cases, put in a piece of clean glass free from scratches or 

 bubbles, and lay the negative upon it. Lantern slides may be 

 printed from a portion of a 4X5 or some larger negative by simply 

 placing the lantern-slide plate over the desired spot. Take great 

 care not to scratch the negative. 



The exposure will be shorter than in case of paper. With an 

 average negative and a gas-mantle lamp at a distance of three feet, 

 try an exposure of 2 seconds; if the negative is weak, shorten the 

 exposure; if strong, lengthen it. 



If a negative is uneven, the distance from the light may be 

 increased so as to lengthen the exposure to several seconds, thus giving 

 time to shade the weak parts, just as in case of prints on paper. 



