122 PHOTO-MICHOGEAPHY 



A specimen of the resulting photograph taken with a photo-achromatic by Wray 

 is shown in Fig. i, Plate III. 



Development. — The general development of a negative has been already given, 

 but to make it more explicit and to save the reader referring back, the process is again 

 given below with certain additions which appertain to the development of photo- 

 micrographical negatives which do not so much obtain with negatives of ordinary 

 subjects. 



It will be best for the beginner to develop each of his plates separately, for which 

 purpose he takes 3 drachms of each solution, details of which have already been given, 

 page 33, 3 drops of bromide solution, filling up to 8 drachms with water. This is the 

 proportion in ordinary cool weather, but when operations are conducted in summer 

 months, when the heat of the dark room is very pronounced, it will be very necessary 

 for the developing solutions to have stood for some hours in cold water, and it will be 

 better to use 2^ drachms of each solution with 3 drops of bromide, filling up to the 

 ounce with water. The gas hght of the dark room should be screened by two layers of 

 ruby fabric, and if the burner be a very bright one, an additional one of yellow. 

 Having wiped the " backing " off the plate, easily done with a wet rag — which should 

 be kept in one corner of the sink — the negative is placed in its developing dish with 

 the sensitive surface upwards, and the 8 drachms of developer flooded over it in one 

 sweep. Till experience is gained it will be frequently found that the plate is not 

 immediately uniformly covered. The dish then should be violently shaken laterally 

 to ensure such a condition, for, if not, a stain will be produced on the final negative, 

 hopeless to remove. The cover to the dish should be at once placed over it and not 

 raised for, say, half a minute, one ruby fabric being removed from the gas. About 

 this time, if the exposure be correct— in cold weather it may be considerably longer — 

 just a faint outline of "something" appearing on the emulsion should be seen. We 

 do not say this will always he the case, but we mean that within half a minute to one 

 and a half minutes there should be some difference shown in the portions of the 

 negative that have been exposed to the light, in contradistinction to those where 

 the light has not reached. The re-covered dish is then rocked steadily to and fro, 

 until slowly and uniformly the image appears. Notice should now be taken as to 

 whether the background appears uniform. If the details rush up with great rapidity, 

 it is a sure sign of over-exposure, and 3, 6, 9, or 12, or even 24 drops of the bromide 

 solution should be rapidly added accordingly. If, however, the strongly-hghted 

 portions of the picture appear grey at first, gradually deepening in density, and the 



