32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 7I 



source. Care was taken to choose angles such that the cone of direct 

 hght included only sky and the reflected light came only from snow. 

 The galvanometer was mounted on a tree about forty feet away and 

 the ammeter and other apparatus was conveniently located nearby. 



Observations were undertaken on two days, February 22 and 23. 

 On the former the sky was very cloudy and snow was falling lightly, 

 so that a thin film of fresh snow covered the patch of old snow. 

 Readings were taken in sets of five except a set of four taken at the 

 end with the instrument pointed at the zenith. Designating the sets 

 alphabetically according to order, we observed as follows : 



a Clouds in southeast, instrument elevated about +45° ; 



h Reflection of clouds of a, instruments elevated — 25° ; 



c Same as a; 



d Same as b; 



e Instrument pointing on snow to southwest, so that direct and re- 

 flected rays would be in vertical plane ; 



/ Clouds whose reflection was observed in ^; 



g Clouds in northeast, about 35° elevation; 



h Clouds directly overhead. 



Sets g and h were taken to give an idea of the comparative uni- 

 formity of the different parts of the sky. 



On the following day there was a cloudless sky. This time light 

 was observed coming from the sun and from the sky 30° around 

 the sun. The day was fairly warm and the snow was melting slightly. 



Ten sets of readings were taken, as follows : 



a Sun and 30° sky around it ; 



b Snow, center about 4^ feet from instrument, giving most direct 

 reflection, as shown by a mirror. 



c Snow, about 30° east of & and 7 feet from instrtiment. 



d Snow, about 30° west of b and 3-| feet from instrument. 



e Snow, about in line with sun and 10 feet from instrument. 



/ Same as a. 



g "Vertical zones," without sun shade (See Zone Observations). 



h Snow, same as e. 



i Mountain side covered with dry grass and leaves, sun almost 

 directly behind instrument. Center of ground about 6 feet from in- 

 strument. 



j Sky directly overhead. Strips shaded from sun by thimble. 



There was an interval of about forty minutes between / and g in 

 order to allow the taking of a holograph. ■ 



Results of the observations are given below : 



