246 president's address. 



focussed, but there is a decided fog all over the whole picture. 

 This is specially noticeable between the dots, and serves to muddle 

 them up in a very disappointing way. When dry, a copy of this 

 is made upon a slow plate, such as a process or a lantern plate, 

 and again developed by time. This becomes our second negative. 

 Even a cursory glance shows at once how much brighter it is 

 than the first taken direct from the object, but when the print 

 or lantern slide is taken from this the improvement becomes very 

 apparent. I may mention that to make the second negative on the 

 slow plate an exposure of from 20 to 60 seconds is required when 

 using the same light as before. I should also mention that the 

 treatment explained is likewise of service in improving contrast, 

 so that both the troubles of the photomicrographer are diminished 

 by one and the same method. 



In conclusion it should be remarked that the treatment 

 suggested must not be considered a " faking " one : it is nothing 

 of the sort, for it is nierety a method of improving the result by 

 photography instead of by changing the methods of the photo- 

 micrographer or seeking the aid of the optician, who admits he 

 cannot help us. 



There is great scope for individuality in applying this method. 

 Some negatives require exactly the treatment mentioned, but 

 others may not be improved unless all the copying is done with 

 slow emulsion, for the fogging may be difficult to get rid of ; 

 whilst even yet another type may not require quite slow plates, 

 being copied throughout by an emulsion which we may call a 

 " medium one." The effect of " overdoing " the method is that the 

 dots appear quite dried up and far too much reduced in diameter, 

 whilst " underdoing " is shown by the process not quite removing 

 the fog. Actual experiment may be required to determine the 

 best means. 



Journ. QueMt Microscopical Club, Ser. 2, Vol. X., No. 02, April 1908. 



