134 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 31 



As a result of these measurements of spectral distribution in the 

 visible and ultra-violet, an invitation has been extended to the divi- 

 sion to be represented on the committee on ultra-violet measurement 

 standards of the Illuminating Engineers Society. Doctor McAlister 

 represented the division in the first of these meetings during the 

 summer, where plans were made for cooperation in the development 

 of suitable standard sources and technique for intensity measurement. 



THERMOCOUPLE TECHNIQUE 



As a result of the development of the specially sensitive vacuum 

 thermocouples by members of the division many requests have come 

 in for the construction of couples for other institutions. This has 

 been possible only in exceptional cases. Couples have been con- 

 structed for the University of California, for the Department of 

 Agriculture, and for the General Electric Co. 



As an adjunct of these highly sensitive couples a special thermo- 

 couple multiplier has been developed which is capable of magnify- 

 ing galvonometer deflections by any desired ratio up to 1,000 times. 

 It has the special advantages of making this magnification linearly 

 for any amplitude and of introducing no appreciable added instabil- 

 ity into the measurements. This technique is applicable not only to 

 the infra-red investigations but also to the phototropic experiment 

 where the measurement of extremely small intensities is required. 



REPORT ON THE WORK OF INDIVIDUALa 



Dr. Earl S. Johnston, plant physiologist, became a full-time mem- 

 ber of the staff in February, 1931. Doctor Johnston began his work 

 with the division as a consultant while still a professor at the Univer- 

 sity of Maryland. He has taken an active part in the plans and de- 

 velopments along the lines of plant physiology almost from the 

 beginning. His addition to the staff has made possible much more 

 rapid progress in the biological phases of the work. He has aggres- 

 sively pushed the phototropic experiments and the wheat experiment, 

 and has assisted in the preliminary growth chamber experiment. His 

 assistance in matters of publication has been very valuable. 



Dr. E. D. McAlister became a member of the staff in September, 

 1930, devoting half of his time to the work of the division and the 

 other half to the work of the Research Corporation. During the 

 latter part of the year all his time was assigned to the work of the 

 division. Doctor McAlister's long experience in thermocouple tech- 

 nique and infra-red measurements makes him unusually well qualified 

 for the work of the division. He has carried out the most exacting 

 phases of thermocouple observations on intensity and wave-length 



