Jan. 25, 1913 
FOREST AND STREAM 
113 
The Effect of a Variable Illumination. 
BY E. J. RENDTORFF. 
In archery as in baseball, golf, football, or 
any of our other standard sports, it is the man 
possessing an intimate knowledge of the little 
details who wins. 
Dr. Hertig writes; “At Thanksgiving I had 
good prospects for straight hits and a score well 
over 500, but at the last a change of light caused 
me to shoot low with the result that my last 
thirty arrows were progressively poor in score. 
I missed with the 79th, 8ist and 83d arrows. 
Then, when it was too late, I found the cause 
and incidentally acquired an item of archery 
lore hitherto unnoticed—that the light may affect 
one's vision so much as to cause a displacement 
of the point of aim. The sun had been shining 
all afternoon, and when it went behind the 
clouds and my point of aim, a light patch of 
grass, receded or rather crept toward me, I 
undershot.” 
The explanation becomes more evident 
through the use of an illustration. 
The amount of this elevation can be learned 
through experience only, as it depends on three 
variables: the acuteness of the archer’s vision, 
the relative darkening, and the nature of the 
point of aim. For a clear cut, distinct point of 
aim, the apparent elevation would be less than 
for a vague, somewhat indefinite “point.” 
One Cause of Failure at Public Meetings. 
In the old Archery and Tennis News for 
Aug. 15, 1882, Launcelot—Will H. Thompson— 
had a very interesting review of the fourth an¬ 
nual meeting of the National Association. This 
drew a letter from Colonel Williams, which ap¬ 
peared in the same paper, Sept. 30, 1882. Mr. 
Thompson wrote: 
“On the last day of the meeting a special 
shoot was arranged at 100 yards for special 
prizes, donated by three archers, and being curi¬ 
ous to study this very matter, I arranged to 
shoot at a target with the champion Homer S. 
Taylor and Colonel Williams. It was at once 
apparent that neither the champion or myself 
trajectory to his arrows, and is the choice quality 
in the shooting. 
“Right here he failed. He would shoot per¬ 
haps six shots with perfect care and most ex¬ 
cellent execution, except at the very last instant 
of the loose, when I could discover a fainting 
of the nerves, as it were, and the arrow went 
on its course with the same line and elevation 
which the archer intended, but dropped just 
under the target or lodged in the black or white 
below the gold. Fully one-half of the shots 
were thus delivered. Occasionally the strong 
will would hold everything taut through the 
critical moment, and the fingers would come 
backward off the string with a firm and rubbery 
tenacity of pull that never ceased its vigor until 
the string had passed the finger tips. In these 
instances there was always the same result. I 
could tell without following the flight of the 
arrow that its destination was ‘a gold, a red or 
at least a blue,’ as Fisher said of Ford’s. 
“Now, Colonel Williams knew that his loose 
was failing him, but why? He could not tell, 
nor yet can I. 
In the diagram E represents the eye, A the 
arrow, B the actual intersection of the line of 
sight with the ground, and C the point of aim. 
When the light is good, the line of sight EB is 
contiguous with the point of aim. We are able 
to “draw a sharp bead” on account of the good 
illumination. We do not cover the point of aim 
with the pile of the arrow, but bring the pro¬ 
jection of the pile in immediate contact with the 
near side of the point of aim, so that it will re¬ 
main in plain view. 
When the illumination is poor the point of 
aim becomes obscured. In order to see it more 
distinctly we unconsciously lower the line of 
sight, as shown in the right hand half of the 
illustration, and allow more of the point of aim 
to lie in front of the projection of the pile. We 
apparently aim as we did before, as the rela¬ 
tive positions of the projection of the pile and 
the point of aim appear the same as they did 
when the light was good. The phenomenon is 
an optical illusion, well understood by physicists. 
The remedy is to apparently raise the eleva¬ 
tion of the arrows when darkness approaches. 
could force our shooting, but Colonel Williams 
began as though the range was under his con¬ 
trol. But despite the low and steady flight of 
his arrows, despite the faultless line kept 
throughout the whole seventy-two shots, and the 
beautiful grouping of his arrows at every end, 
either just under or just over the target, the 
scoring was very poor for even a mediocre 
archer, much less such an one as Colonel Wil¬ 
liams. 
“I readily discovered the immediate cause of 
the faiure in keeping the elevation, but I could 
not tell the cause of the cause. 
“The perfect elevation is of course only to 
be kept by an unvarying draw and unvarying 
loose. The drawing of Colonel Williams was so 
exactly the same at each shot that only in one 
instance did I think I detected a variance, but 
the loose was defective. In practice this gentle¬ 
man’s loose is nearly perfection. His fingers 
are pulled smoothly and steadily backward off 
the string with a rather slow, firm and perfectly 
resolute movement. It is the constant pulling 
until the string is gone, which gives the flat 
“Now, the failure of the loose in his case 
was only partial. It was not only at the latter 
part of the loose, but at the very last of it. In 
a flight of sixty yards the results would have 
been very little worse than if the loose had been 
perfect, but at 100 yards the error was fatal. I 
think many of our archers are troubled in the 
same way, and communications on this point 
would be valuable and interesting. Will Colonel 
Williams, Mr. Walworth, Mr. Hammond, Mr. 
Taylor, Mr. Nash and other gentlemen give us 
some notes upon the subject through the Archery 
and Tennis News?” 
Colonel Williams’ “Notes’’ follow: 
Editor Archery and Tennis News; 
In your issue of Aug. 15 appears an article 
from Launcelot in which he refers at some 
length to my shooting at Chicago in July last. 
He has discovered the cause of my indifferent 
score at the York round, but was unable to de¬ 
termine the cause of the cause, and calls for 
further information on this point. 
The cause of this cause was partly lack of 
muscular and nervous force, and partly a lack 
