IOWA ACADEMY OF SCIENCE 
287 
brought out by these is the fact that there is no difference between those 
taken with the diffused light from behind and those illuminated from 
the front. This is an important point for it proves the assumption which 
I made early in the paper. 
As I have already explained, this diffused light from the back was 
obtained by placing an incandescent light covered with ground glass, in 
the place of my point source. To get the illumination in front, I moved 
this light in front and a little to one side of the object, removed the 
lens, and placed just back of the object a piece of white card board 
which acted as a background. The removal of the lens did not change 
the optica] conditions in any way. 
You will notice that what would have been No. 37, which would have 
been taken with reflected light with the 2.5 in. telescope is missing. I 
made several attempts to get this picture but could get no effects. I 
made one exposure of eighteen hours but got no fogging of the plate. 
After making one hundred forty different exposures and studying 
them carefully I have come to the conclusion that astronomers can 
see, without question, certain details upon the planet Mars. While I 
do not have absolute evidence, yet I also believe that there is very little 
advantage in using a telescope larger than twenty-four inches for ob- 
taining details of objects as large as 20 miles across. 
For fear that I may be misunderstood I want to say that I have 
not taken into account the different atmospheric conditions with which 
the astronomer has to contend. I wish to state also that this investi- 
gation does not apply alone to the planet Mars but may he applied to 
the study of any illuminated surface. 
My work is by no means completed. I expect to continue by in- 
vestigating smaller details upon my object and by varying the atmos- 
pheric conditions and noting the effects produced. 
In closing I wish to express my thanks to Dr. L, P. Sieg for the val- 
uable advice he gave me during the course of my work and for the as- 
sistance he rendered on many occasions. 
