BOTANICAL PHOTOGRAPHY 171 



Intensifying underexposures. — Even if a negative or lantern slide 

 has been considerably overexposed, it can be reduced quite satis- 

 factorily; if much underexposed, httle can be done for it; if only slight- 

 ly underexposed, it may be greatly improved by the following solution : 



Metric Apothecaries' 



(Bichloride of mercury 2 g. (31 gr.) 



Water 100 c.c. ( 4 oz.) 



Bromide of potassium 2 g. ( 31 gr.) 



J Sulphite of soda crystals 10 g. (154 gr.) 



\ Water 100 c.c. ( 4 oz.) 



The solutions keep indefinitely and may be used three or four times. 



Apply the intensifier after fixing in hypo and washing in water. If 

 the negative or slide has been allowed to dry, soak it in water for half 

 an hour before intensifying. 



Place the negative or slide in A, rocking the tray as in developing, 

 until it becomes gray or even white. Wash in water for 5 minutes and 

 then transfer to B and leave until the dark color can be seen on the 

 back of the negative or slide. Wash in water as thoroughly as after 

 fixing in hypo. 



Some use a saturated aqueous solution of the bichloride of mercury, 

 without the bromide of potassium; and, instead of solution B, use 

 water to which ammonia has been added — about 1 part ammonia to 

 40 parts water. Excellent sepia tones may be secured in this way. 

 Wash well in water. 



After the plate has been thoroughly washed in water, wipe it gently 

 with a tuft of cotton. The cotton must, of course, be thoroughly wet; 

 it is better to hold the plate under a stream of water while wiping. 

 This should always he done before placing a negative or slide in the rack 

 to dry, after a washing in water. 



PHOTOMICROGRAPHS 

 By Dr. Paul J. Sedgwick 



For the making of photomicrographs at the highest magnifications 

 a regular photomicrographic camera, consisting of a heavy, rigid, 

 optical bed to which are attached the camera proper, the microscope, 

 the condensing lenses, the filters, and the light source, is almost a 

 necessity. Such an outfit certainly facilitates the making of photomi- 

 crographs at any magnification, and the worker who is required to 

 make any considerable number of photomii'rographs should be so 



