ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 



707 



Methods of Producing Enlargements and Lantern Slides of Micro- 

 scopic Objects for Class Demonstrations.* — The method practised by 

 J. Aspinwall is the result of an attempt to produce pbotomicrographs 

 of considerable magnification, and yet of great depth of focus, while 

 using lenses of high resolving power. Use an objective of medium 

 power, say a -\ in., making the negative of a diameter of 11— 2 in. In 

 a lantern-slide camera enlarge from one-half to three-quarters of the 



Fig. 161. 



central area of the negative to twice its diameter on a Paget lantern- 

 slide plate. By another enlargement from this positive a negative of 

 any diameter can be secured. The enlarging lens must be well stopped 

 down. In making the original negative use an objective without the 

 ocular, and, instead of the substage condenser of high angle, an ordinary 

 objective, say, of 1 in. focus, with a beam of light at a very low angle. 



* Trans. Amer. Micr. Soc, sxii. (1901) pp. 41-7. 



