Photograpbiiig Fish 213 



color values. They are somewhat slower than 

 the ordinary fast plate, and this must be taken 

 into consideration, but it is entirely compensated 

 by the superior quality of the negative which we 

 are enabled to obtain with them. 



When the fish to be photographed will remain 

 quietly in one position for a long enough time 

 to allow us to do so, the very best results can 

 be obtained by the use of the slow isochromatic 

 plate in conjunction with the ray filter; but such 

 fishes are few and far between, and we must not 

 expect to find them often. 



One of the greatest obstacles with which one 

 has to contend in this work is the difiiculty of 

 getting perfectly clean, clear water and keeping 

 it in this condition. Of this Mr. Dugmore, who 

 has done probably the best work on fishes of 

 anybody in this country, or elsewhere for that 

 matter, has considerable to say, and, as he is 

 undoubtedly an authorit}^ I will quote him : — 



" Absolute clearness of water is highly desir- 

 able but almost impossible to obtain. After 

 straining the water so that it is clear enough for 

 ordinary work in a good light take an apparently 

 clean stone, not a smooth marble of course, but 

 an ordinary moderately rough stone, drop it in 

 the acjuarium, and watch the result. The water 

 will be seen to be filled with a muddy substance, 

 and, instead of crystal-like clearness, we have a 



