NO. IO REFLECTING POWER OF CLOUDS ALDRICH 3 



ARRANGEMENTS 



Pyranometer A. P. O. No. 5, modified for use in the eclipse expedi- 

 tion of June 8, 1918, 1 was somewhat further modified for this work. 

 It was proposed to suspend the pyranometer, inverted, below the 

 basket of the balloon, thus exposing the pyranometer strip to the 

 radiation from a practically infinite cloud surface. The sun shade 

 was removed and the glass hemisphere securely fastened in place 

 with shellac. The pyranometer was suspended about one-half meter 

 below the bottom of the balloon basket, and a flexible shaft, operating 

 the shutter through miter gears, extended to within easy reach of the 

 officer in the basket. For stability the galvanometer was necessarily 

 mounted on the ground and connected to the pyranometer through 

 a reel of special telephone wire. (Insulated piano wire was employed 

 such as is used in ordinary balloon work for telephone communica- 

 tion with the ascending officer. This introduced probably over 

 1,000 ohms resistance into the galvanometer circuit, but the pyran- 

 ometer was sufficiently sensitive to give deflections ranging from 

 1.50 to 4.0 cms. and could be read to 0.01 cm.). The galvanometer, 

 ammeter, and accessories were the same as used on the eclipse ex- 

 pedition of last June, 1918. 1 



Observation Balloon No. 7, with its complement of officers and 

 men, was assigned to aid in the work. The writer wishes to express 

 his appreciation for their assistance, and particularly for the interest 

 and efficient help of Lieut. E. W. Raeder, the ascending officer. 

 Lieut. Raeder reported the sky conditions and manipulated the 

 pyranometer shutter from the balloon basket, being in constant 

 telephone communication with the ground through a second reel of 

 telephone wire. His great zeal and gallantry are shown by the fact 

 that, being alone in the basket, he tied his ankle by a bit of rope to 

 the balloon and hung head downward for about 5 minutes to fix a 

 defect in the exposing apparatus which developed near the end of the 

 experiments, then climbed back and continued the observations. 



OBSERVATIONS 

 The observations of cloud, sun, and sky, and of electric current for 

 calibration of the pyranometer, are given in Table I. As the balloon 

 was brought to earth between observations of groups 7 and 8 (see 



1 See Smithsonian Misc. Coll., Vol. 69, No. 9. 



