Getting Organized -23- 



cloud-chamber technique. Also a very simple pocket-size unit was devised 

 for making spot checks of the relative numbers of such nuclei in a given 

 sample. 



Vortex Thermometer . A development of much significance was the 

 design by Vonnegut of an instrument, the vortex thermometer, for use by 

 airplanes in measuring true air temperature. '"") The usual type of ther- 

 mometer is unsatisfactory for this purpose because of aerodynamic heat- 

 ing caused by the rapid movement of the airplane through the air. The 

 vortex thermometer reduced these aerodynamic effects to a negligible 

 amount. Also, for the first time , it made it possible to give a quite accu- 

 rate measurement of the temperature in a cloud. Furthermore, an indica- 

 tion of true air speed can be provided by measuring the difference in 

 readings given by a vortex thermometer and one exposed in the normal 

 manner, because the deviation from true temperature of a normal ther- 

 mometer varies with the speed of the plane. Eut it was found that the 

 vortex whistle (see below) showed greater possibilities for this application. 



Vortex Speed Indicator . An outgrowth of the development of the 

 vortex thermometer was the adaption of the principles involved to the 

 production of a musical note (Vonnegut). As the pitch of the note produced 

 in such a manner varies with pressure, such a whistle could be used as 

 the basis for measurement of true air speed and air mileage of airplanes.'' *■' 



Rain Catcher . A tool found very useful in rain studies aloft was a 

 rain catcher, developed (Langmuir-Schaefer-Maynard) to give the average 

 value of the precipitation in the air for approximately each thousand feet 

 of flight. The device involves the use of a rain scoop, a tube whose exit 

 velocity can be controlled, and a group of storage containers. (82) 



Portable Cold Chamber . A simple but effective cold chamber was 

 designed by Schaefer, which could be carried about for field studies. It 

 consisted of a small rectangular wooden box lined with copper sheeting 

 and having a copper inner chamber. A charge of five pounds of crushed 

 dry ice was found to hold the temperature below -10°C for three 

 hours> 3 ' 84 > 86 ) 



Ice Nuclei Detectors . Since one of the important properties of the 

 atmosphere as related to the persistence of supercooled clouds is the 

 presence of ice -forming nuclei, considerable effort was expended toward 

 the development of an instrument which would provide a continuous, auto- 

 matic record of the quantity of such nuclei in the air at any given time. 

 Two developmental instruments were devised, but difficulties were expe- 

 rienced with both of them, and neither was brought to a satisfactory 

 dfegree of perfection. One device (Schaefer) made use of the tendency 



