REPORT OF THE SECRETARY 135 



distribution in the phototropic experiment. He has materially con- 

 tributed to the development of the preliminary growth chamber and 

 controls. He has carried out an investigation on the distribution of 

 the mercury arc in the blue and ultra-violet. He has furthermore 

 handled a large }>art of the technical developments of thermocouples. 

 This is in addition to his work with the Kesearch Corporation, for 

 which he has carried out exhaustive investigations of the possibilities 

 of the thermopile for use as a source of electromotive force in ap- 

 plied fields. He has carried out preliminary developments of the 

 nephylometer for general experimental use. 



Leland B. Clark, in addition to carrying on all the regular ghass- 

 blowing, lias handled tlie vacuum technique development in connec- 

 tion with the thermocouples. He has constructed a practical butjdph- 

 thalate pump of original design. His assistance in many phases of 

 special laboratory technique is of great value to the division. 



William H. Hoover has carried out a large part of the equipment 

 and operation of the preliminary growth chamber; he has adjusted 

 and increased the sensitivity of the carbon dioxide detecting device 

 loaned to the division by the Fixed Nitrogen Research Laboratory 

 and he has installed and put in operation temperature-control equip- 

 ment for the individual wheat experiment. He has designed and in- 

 stalled a new thermostat which greatly increases the stability of the 

 carbon dioxide recording mechanism. This is in addition to his 

 work with the Astrophysical Observatory, for whom during the year 

 he has spent a month in the development of photometric equipment 

 and two months on a trip to Table Mountain, as well as some com- 

 putational work on the annual report. 



Miss Stanley, in addition to the regular stenographic work, now 

 a considerable load, has ably handled all our bookkeeping in con- 

 nection with purchases. 



L. A. Fillmen, a mechanic of wide experience in apparatus and 

 equipment construction, became a half-time member of the staff in 

 August, 1930. His experience and ability have contributed largely 

 in the development of equipment for the laboratory. Through the 

 courtesy of the Fixed Nitrogen Kesearch Laboratory, Mr. Fillmen 

 worked for several months in their shop while our shop was being 

 equipped. 



PERSONNEL 



During the fiscal year the personnel was as follows : 

 Chief.— Dv. Frederick S. Brackett. 

 Research associate. — Dr. Earl S. Johnston. 

 Associate research assistant. — Dr. E. D. McAlister. 

 Research assistant assigned hy the Astrophysical 0})servatory. — 

 W. H. Hoover. 



