MICROSCOPIC OBJECTS. 



21 



and no choice seems to be left but to 

 under-print some portions, and over-print 

 others. In this case, good prints may gen- 

 erally be obtained by the judicious applica- 

 tion of cotton-wool. When the quick 

 printing portions are done, cover them with 

 cotton-wool, place the printing-frame in the 

 sun, and print in the denser parts as quickly 

 as possible. In the finished print there 

 should be no mark left by the wool, but all 



should appear as if printed in at the same 

 time. The writer once photographed a 

 section — transverse — of hazel, which was 

 thicker one side than the other. As the 

 negative showed splendid detail he did not 

 like to destroy it, but made use of cotton- 

 wool, covering the weak part, corresponding 

 to the thicker side of the section, witli cot- 

 ton-wool as soon as sufficiently printed and 

 leaving the dense part, which corresponded 



HEAD AND JAWS, GARDEN Sl'IDER. 



to the thinner side, to print furl her in a 

 strong light. In the finished print there 

 was not the slightest indication of the un- 

 equal density of the negative. 



Very dense negatives should always be 

 printed in strong sunlight ; but as such neg- 

 atives always give harsh prints, they should 

 always be reduced to a proper density by 

 the ferricyanide reducer. Some, however, 

 are not injured by excessive density. The 

 density that would ruin a portrait or land- 

 scape negative may pass unnoticed in a pho- 



to-micrograph, or, perhaps, be even an im- 

 provement. The chief objection to dense 

 photo-micrographs is that they print very 

 slowly, but in the majority of cases this will 

 be no serious defect. The figure of a spi 

 der's head, given above, is from a very dense 

 negative, which prints very slowly, but oth- 

 erwise is satisfactory. 



Thill delicate negatives should be printed 

 in the shade. The application of matt-var- 

 nish or tissue paper to the back of the neg- 

 ative will frequently improve the quality of 



