52 



Journal of Applied Microscopy. 



tally; but the granules creep through 

 the mountings again if the stage is 

 placed vertically. 



The photographs accompanying this 

 paper were made from samples mounted 

 in glycerine jelly. Care is needed to avoid 

 air bubbles, and I have found it best to 



distinct outline, the whole field deteri- 

 orates and a sharp negative becomes an 

 impossibility. The non-actinism of yel- 

 low light precludes its use, otherwise 

 beautiful contrast can be had with 

 sodium flame. I have found that the 

 interposition of a sheet of deep blue (co- 



Fig. 1. 



Fis. .".. 



pass the sample after grinding through a 

 sieve of one hundred meshes per inch, 

 making a separate examination under a 

 lower power, of the coarser portion, the 

 result of this examination being taken 

 into consideration in reporting upon the 

 sample. 

 I have used an alternating arc lamp 



bait) glass, very much improves the con- 

 trast, and it is with such an arrange- 

 ment that the accompanying photo- 

 graphs have been made. I do not doubt 

 that a cell filled with ammonia-copper 

 sulphate would answer the same pur- 

 pose, but there is a pleasure in working 

 with dry solid materials, which makes 





H-''^" 



Fijj. 2. 



FiK. 1. 



using fifty-two volt current and supplied 

 with automatic- centering arrangements, 

 and the illuminating and condensing sys- 

 tem supplied by Bausch & Lomb. Owing 

 to the varying refrangibility of white 

 light, an absolutely dark field is impossi- 

 ble, and although this is not of much 

 consequence in ordinary work, it is very 

 troublesome in photography; since, if 

 the exposures be long enough to give a 



the glass preferable. The microscope is 

 a Zeiss instrument, and I use an apo- 

 chromatic of 16 mm. focus with compen- 

 sating eyepiece No. 4. A camera of about 

 33 inches gives 22.5 diameters with this 

 combination, and I find that to be a very 

 satisfactory magnification, when a nega- 

 tive 4x5 is required and the field photo- 

 graphed is well filled. 



