Early History -5- 



In the course of this work, Schaefer relied heavily on the services 

 of Raymond E. Falconer, who was then one of the observers in the weather 

 station on the summit. 



AIRCRAFT ICING 



It so happened that the Army Air Forces were just as much interested 

 in problems of aircraft icing as in precipitation static. This fitted in so well 

 with the new interest of Langmuir and Schaefer that in 1944 they started a 

 study of icing of aircraft. ^^) 



They had much assistance from Victor Clark, Falconer, and others 

 of the observatory personnel, who were already working on riming and 

 icing. Langmuir and Schaefer, however, were able to introduce some new 

 and very productive ideas. 



Extensive mathematical calculations were necessary. The first work 

 of this nature was done by Langmuir, and his results were used in connec- 

 tion with the cloud studies at Mount Washington (see below). During the 

 later stages of the Mount Washington studies, Langmuir decided to make use 

 of a differential analyzer for these calculations, and in preparing the mat- 

 erial for that purpose, he was assisted by Dr. Katharine Blodgett. Thus 

 it was possible to calculate the percentage of water droplets which would 

 be deposited on a given surface under specific conditions. The information 

 was used on data obtained on Mount Washington to determine the number 

 and size of water droplets involved in the formation of ice. 



CLOUD STUDIES AT MOUNT WASHINGTON 



The theoretical calculations worked beautifully in practice. They 

 began to acquire a very satisfactory understanding of some features of 

 cloud structure and the growth of cloud particles. They became absorbed 

 in this new interest. And Langmuir found he could apply to his smoke gen- 

 erator work the same evaporation-condensation theory he had used to cal- 

 culate the growth of smoke particles.' HA) 



But, although they felt they had a fundamental theory for some of the 

 factors that caused particles to grow in clouds to the size they are, they 

 didn't feel conditions were right for further study on Mount Washington. 

 It would be far better to study cloud particle growth in airplane flights. 

 That would require the development of new instruments. 



This was late in 1946. They took the question up with the Army Air 

 Force and the Signal Corps. They were led to think that perhaps some- 

 body might furnish aircraft for experimental purposes of this sort; it 

 seemed that it would be desirable to know something about clouds from a 



