The results of these tests show that if raw hide is to be used as a backing, it should be kept as thin as possible. The sample that was used in the test was almost 1/16th of an inch in thickness. A thickness of 1/64th of an inch would probably answer just as well as far as preventing the bow from breaking is concerned, and would not reduce the efficiency nearly so much as the thick raw hide.
Judging by the general shape of the acceleration curve for all of the various bows which have been tested in the laboratory, it is believed that there is an opportunity of further increasing the efficiency of a bow by changing its design. The acceleration curves are too steep at the beginning and do not hold up well enough toward the end. It is believed that this condition can be improved.
The use of the spark chronograph was found so valuable by Dr. Hickman that he designed a portable chronograph based on this principle which could be used either on A.C. or D.C. current. This chronograph was described in the Jan. issue of the Journal of the Franklin Institute in 1931. The model made by Dr. Hickman was used extensively for testing bows and arrows up until 1940. When he was placed in charge of rocket development by the NDRC, he made use of the chronograph for measuring the velocity of rockets in flight. The instrument was in continuous use until 1945. He will, no doubt again make use of it in connection with further investigations of bows and arrows. Since this magazine is available in most libraries this article is not included in this book.