234 PHOTOMICROGRAPHY 



papers, and prints are obtained on them by contact, 

 reduction, or enlargement, in exactly the same way. 

 Equally good lantern slides can be made on the fast and 

 slow plates, provided the exposures are accurately 

 gauged and development is carried to the right point, 

 which is easily learnt by examining a few trial slides in 

 the hand and in the lantern. 



The Paget Prize Plate Co. have introduced a lantern 

 plate called the " Hydra Lantern Plate," which can be 

 printed-out in daylight and treated in the same way as 

 a self -toning paper. It gives very bright slides and is 

 less troublesome than gaslight printing and development, 

 particularly when only odd slides are required. 



Lantern Slides by Reduction. Lantern slides are often 

 required from negatives or parts of negatives of greater 

 area than the lantern plate, and these must necessarily 

 be made by reduction. Any of the enlarging apparatus 

 described can be used for this purpose by reversing the 

 relative distances between the lens and the negative on 

 one hand, and the focussing screen on the other, and 

 adjusting the two until the required reduction is obtained. 

 The dark slide is fitted with an adapter to carry the 

 lantern plates. Fast lantern plates are the most con- 

 venient, and require very short exposures with a good 

 light and condenser. Fifteen seconds to a minute or two, 

 according to the density of the negative, will suffice with 

 the reflecting arrangement of Fig. 70 and two 32 c. p. lamps. 

 If daylight or a good illuminant and condenser is used the 

 exposures just mentioned are sufficient for the slow plates. 



After -Treatment of Lantern Slides. Lantern slides 

 must be bright, clean, and delicate, and with practice 

 good ones can be made with certainty ; but sometimes 

 it is desirable to correct defects. Thin and flat slides can 

 be improved by the methods of intensification given on 

 page 227, while dense or fogged slides may be brightened 

 by a short immersion in Howard Farmer's reducer. 



