WITH THE MICROSCOPE. 269 



and pour on again ; repeat this several times, just holding the plate 

 in the intervals between the eye and lamp, to judge of the increased 

 intensity, which, when it appears sufficient, should in the darkest 

 parts permit the flame of the lamp or yellow window, to be just 

 seen through. Now wash well with water, finish with a little soft 

 water ; with a small towel wipe the back, and set the plate to drain 

 in a plate rack, attaching to the lower corner a small piece of blotting 

 paper, or the plate can be dried off at once over the lamp. It is 

 sometimes difficult to judge of the real intensity gained under this 

 treatment, when the image is observed by yellow light, therefore, 

 after the flowing over of the iodide of potassium solution, the re- 

 mainder of the operations can be conducted by the direct light of 

 the small lamp, or any moderate diffused light. 



Should the development have been carried a little too far, or 

 should the fine transparent markings appear thickened or clouded, 

 before setting up the plate to drain, flush it with a mixture of 

 equal parts or the cyanide and iodide solutions and distilled water, 

 then well wash. Under this treatment many of the minute spots and 

 half-toned points become remarkably brightened. Some prefer to 

 intensify before using the cyanide solution, by, first, under non-actinic 

 light, after the iron developer has been well washed from the plate, 

 pouring on the pyro solution, with a little alcohol, returning it to the 

 developing glass, then adding the mixed silver solutions and repouring 

 on and off the plate, until the image has been brought up to the 

 necessary intensity, when it is to be well washed, and then treated 

 with the hypo-fixing solution or the cyanide. Or the operator may 

 proceed to intensify after well washing off the iron solution, after 

 clearing by cyanide or hypo solutions, using the pyro and silver 

 solutions, without the previous use of the iodo-iodide of potas- 

 sium solution. The fixing solutions are returned to their vessels 

 (short wide-mouthed bottles or jugs are convenient), and can be 

 used over and over again, adding a fresh quantity as occasion may 

 require; but the cyanide solution must not be left exposed, for 

 it soon loses cyanogen, and the vapours are deleterious. Keep the 

 hands continually wiped in these operations. If the plate, after the 

 application of the iron solution and cyanide solution, have the appear- 

 ance of under exposure, the image indistinct in detail or of being over 



exposed, the image of a too dark and uniform character throughout 



or of being out of focus it will not be worth while to proceed to further 

 develope it : wash it and carry it to the light, examine it with the hand 

 magnifier, as some part, not that specially focussed, may appear the 

 sharpest and serve to indicate the alteration required on re-focussing. 

 If any extraneous light should have entered, through defects in the 



