92 Mr. J. C. McConnel on the 



Observations at St. Moritz. 



Most of my observations were taken at St. Moritz during 

 the autumn of 1887. For a proper appreciation of them 

 some description of the country is necessary. The Engadine 

 may be roughly represented by a straight neai'ly level trough, 

 running from south-west to north-east, whose steep sides are 

 about three thousand feet high. On either side of the trough, 

 especially on the south, there are extensive mountain-ranges. 

 The place of observation, viz. the Kulm Hotel, is situated on 

 the northern slope, about 300 feet above the bed of the valley 

 and 6000 feet above sea-level. Immediately below, the bed 

 of the valley is occupied by a lake above half a square mile 

 in area. On October 20th the snow covered the opposite slope, 

 coming right down to the water's edge, though the uniform 

 whiteness was a good deal broken by woods. The northern 

 slope was nearly free from snow up to perhaps 8000 feet 

 above sea-level. 



All the observations refer to points ninety degrees from 

 the sun, and, unless the contrary is stated, to the highest of 

 such points in a cloudless sky. The chief results are 

 numbered 1, 2, 3, 4. G denotes the angle of incidence on 

 the five plates when neutralization takes place ; r and s are dif- 

 ferent measures of the polarization defined above. The manner 

 in which they are derived from G is explained below under 

 the heading Standardization. The error in r, due to bad 

 setting of the pile, is not likely to exceed '01 except when Gr 

 is greater than 55°, and the probable error in standardization 

 is of about the same magnitude. 



1. The polarization is weakest towards noon. 



October 21. 

 G. r. s. 

 9.0 A.M. 53° -209 -53 

 9.20 5H -221 -57 



12.55 P.M. 501 -228 '59 

 3.50 Too great to be measured. Sun just setting be- 

 hind hill. 

 3.55 611 -156 -37 Inclined to right. 



The last measure was only a rough estimate, as the pola- 

 rization was so strong. The instrument was pointed over the 

 mountains to the right, which were in full sunshine. The 

 polarization then was not so strong as at the highest point 

 (see 2). 



