PRACTICAL PHOTOMICROGRAPHY. 99 



High lights dense black, shadows dirty grey under- 

 exposure. 



High lights appear after fifteen to thirty seconds, grey at 

 first, gradually darkening, shadows creeping up steadily all 

 the time; finally high lights black and shadows ranging 

 from pale to dark grey correct. 



High lights rapidly followed by shadows, the whole rapidly 

 gaining great blackness and density overexposure. 



High lights and shadows appearing almost immediately and 

 simultaneously, the whole turning rapidly gray and remaining 

 so great overexposure. 



Instant flashing out of the whole image, all remaining a 

 very pale smokey grey enormous overexposure. 



THE HYDROQTJINONE DEVELOPER.* 



This system of development has of late been greatly 

 elaborated and improved, especially since it was found 

 feasible to use hydroquinone in conjunction with the hydrate 

 or caustic alkalis without damage to the film. Whether or 

 not this is destined to be the standard developer of the future, 

 we are confident in stating that it is a very fine developer at 

 present. Indeed, on account of the ease with which almost 

 any amount of density may be obtained without injury to the 

 shadows, it is probably the best developer for photo-micro- 

 graphic negatives. A further advantage is that this developer 

 can be used without the presence of soluble bromides. "We 

 give a formula due to Messrs. Thomas & Co., of London; 

 though containing a heavy dose of hydroquinone, it is not 

 really expensive, as one dose of the developing solution may 

 be used for three, four or even more plates. The formula 

 stands thus : 



a. Sodic sulphite 1 ounce 



Citric acid 30 grains 



Amm. Bromide 10 grains 



Water to , . . 10 ounces 



Dissolve and add hydroquinone 80 grains 



* It is to be hoped that hydroquinone will soon be universally called 

 by its shorter and systematic name : " Quinol." 



