BOTANICAL PHOTOGRAPHY 181 



fast to be studied at normal speed and in the speeding up of action that 

 is too slow to be studied at normal speed. The following table will indi- 

 cate the apparent rate of action as seen on the screen according to the 

 rate at which the frames were exposed in the camera. 



Rate of Exposure of Frames Rate of Action on Screen 



128 frames per second | normal 



64 frames per second j normal 



32 frames per second | normal 



16 frames per second normal 



8 frames per second 2 times normal 



1 frame per second 16 times normal 



1 frame per minute 960 times normal 



1 frame every 4 minutes 3,740 times normal 



1 frame every 6 minutes 5,760 times normal 



1 frame every 10 minutes 9,600 times normal 



1 frame every 15 minutes 14,400 times normal 



PHOTOGRAPHIC FORMULAS 



The makers of photographic plates, films, and papers know what 

 they have put into their emulsions and, consequently, it is better to use 

 their formulas in developing their products. 



In making solutions, dissolve the ingredients in the order in which 

 they appear in the formulas, making sure that each one is dissolved 

 before another is added. Remember that metol should be dissolved in 

 warm water. A vigorous use of the stirring rod is always worth while 

 and, with sodium sulphite or sodium carbonate, a hard cake will form 

 unless the salts are added slowly with constant stirring. If metol is 

 not completely dissolved before the sulphite is added, they combine 

 and form an inert mass which makes the developer just that much 

 weaker. Use distilled water whenever possible. When distilled water 

 is not available, boil the water — but not in an iron kettle — and then 

 cool and filter it. 



Ingredients of formulas. — Many of the formulas in common use 

 have the same ingredients, but in different proportions. Those in most 

 common use are metol, hydrochinon, pyrogallic acid, pyrocatechin, 

 sodium sulphite, sodium carbonate, and potassium bromide, with 

 potassium metabisulphite, carbonate of potassium, sodium sulphide, 

 acetone, sulphuric acid, and citric acid appearing less often. 



Hyposulphite of soda, commonly called "hypo," with or without a 



