APPARATUS AXD MATERIALS. 19 



sufficiently exposed, the time taken in development will 

 depend mainly on the developer employed, but also on 

 the leisure at the operator's disposal. With a suffi- 

 ciently exposed negative it is possible to spend five 

 minutes or fifty in the dark room, without any appre- 

 ciable difference in the result. Generally speaking, the 

 naturalist will find that he has little time to waste over 

 minims of A, B, or C. What he wishes to get at is the 

 knowledge as to whether he has failed or succeeded. 

 Half-an-hour spent over a plate before one can realise 

 that there has been such movement on the part of the 

 subject as to render the negative useless is a pure 

 waste of time. In a subsequent chapter the reader's 

 attention will be directed to the kind of movements 

 referred to, and to the difficulty of detecting them at 

 the moment of exposure. Again, if time must be 

 spent on experiment, the naturalist will find it profit- 

 able to deduct twenty minutes from the time spent in 

 the dark room, and to spend those minutes in exposing 

 a few more plates outside. It must never be forgotten 

 that a dozen plates are a cheap price to pay for a good 

 natural history photograph. 



It must not be assumed that, in the foregoing 

 paragraphs, the writer wishes to suggest that tentative 

 development is a useless proceeding. Nothing could 

 be farther from his thoughts. He wishes rather to 

 emphasize the fact that to secure a negative giving 

 detail, density, and gradation a negative, that is, which 

 may be valuable it is the exposure, and not the 

 development, that is of paramount importance. 



