72 — Twelve on the screen. 
more useful than King’s, because our methods are, perforce, quite 
different. He is photographing more or less all the year round, 
and with constant practice turns out a properly exposed negative 
without being afterwards able to give you details about light, stop 
or shutter speed. I, on the other hand, am restricted to about 
a fortnight each year; therefore I have to pay great attention to 
detail in order to get good results. He is like the normal individual 
who can rise from his chair and walk out of the room without 
thinking of how it is done. I am like the poor man with locomotor 
ataxia, who has to repeat to himself, ‘‘ Now I must bring my feet 
back under the edge of the chair, now I must lean forward and 
straighten my hips as I straighten my knees.” Accordingly I use 
a Watkin’s standard meter, which looks complicated, but is soon 
learnt, and test the light whenever I can. For birds at close 
quarters I always use 100 as the subject number. The only thing 
I have found of any use with under-exposures is to first of all 
harden the film with formalin and then develop at a temperature 
of about godeg. Fahr. Of course, every fresh bird that you try 
has some characteristic which has to be studied; that is where 
some of the sport comes in. The stumbling block in the case of 
adult Peregrines is the extreme rapidity of the sudden turn of the 
head. Instead of trying to overcome this by brute force, by 
giving an extremely short exposure, it is better to wait for the turn 
and expose directly it is over. 
Photographs being more useful scientifically if taken to scale, 
I have a piece of broomstick with sixteen inches prominently 
marked on it. When placed on rock C and focussed on the screen 
it was found that a halfpenny (one inch in diameter) covered five 
inches on the broomstick, so that the bird photographed on C 
would be a fifth of life-size, and in afterwards making an enlarge- 
ment, if I enlarge the image on the negative five times I get the bird 
life-size. On B the halfpenny covered six inches, showing that 
the bird would then be a sixth life-size on the negative and in the 
middle of the eyrie a seventh. As nearly all the illustrations are 
enlarged, I might state that the largest image among my Peregrines 
is that of the Peregrine stretching himself. This on the negative 
measures three and a-half inches from the top of his head to the 
