EXPEDITION TOWARD THE NORTH POLE. . 375 



rounded masses, or in regular crystals; also the conditions under ^ybieb 

 these difl'erent forms are produced. 



The form and weight of hailstones should be noted, whether consist- 

 ing of alternate strata, the number of which is important, of flocculeut 

 snow, or solid ice, or agglutinations of angular crystals, whether of a 

 sphericril form, or that of an obhite spheroid. 



The color of the snow should be observed in order to detect any 

 organism which it may contain, and also any sediment which may re- 

 main after evaporation, whether of earthy or vegetable matter. 



Clouds. — The character of the clouds should be described, and the 

 direction of motion of the lower and higher ones registered at the 

 times prescribed for the other observations. Since the expedition is 

 well supplied Avith photographic apparatus, frequent views of the 

 clouds and of the general aspect of the sky should be taken. 



Aurora. — Every phase of the aurora borealis will of course be re- 

 corded ; also the exact time of first appearance of the meteor, when it 

 assumes the form of an arch or a corona, and when any important 

 change in its general aspect takes place. The magnetic bearing of the 

 crown of the arch, and its altitude at a given tune, should be taken ; 

 also, if it moves to the south of the observer, the time when it passes 

 the zenith should be noted. The time and position of a corona are 

 very important. 



Two distinct arches have sometimes been seen co-existing — one in the 

 east and the other in the west. In such an exhibition the position and 

 crown of each arch should be determined. Drawings of the aurora, 

 with colored crayons, are very desirable. In lower latitudes a dark 

 segment is usually observed beneath the arch, the occurrence of which, 

 and the degree of darkness, should be registered. It also sometimes 

 happens that a sudden precipitation of moisture in the form of a hazi- 

 ness is observed to cover the face of the sky during the shooting of the 

 beams of the aurora. Any appearance of this kind is worthy of atten- 

 tion. 



Wave motions are sometimes observed, and it would be interesting to 

 note whether these are from east to west or in the contrary direction, 

 and whether they have any relation to the direction of the wind at the 

 time. The colors of the beams and the order of their changes may be 

 important in forming a theory of the cause of the phenomena. Any 

 similarity of appearance to the phenomena exhibited in Geissler's tubes 

 should be noted, especially whether there is anything like stratification. 



The aurora should be frequently examined hy the spectrosco[)e, and 

 the bright lines which may be seen carefully compared with one of 

 Kirchofl's maps of the solar spectrum. 



To settle the (piestion as to the fluorescence of the aurora and its con- 

 sequent connection with the electric discharge, a cone of light reflected 

 from the silver-plated mirror should be thrown on a piece of white paper, 

 on which characters have been traced with a brush dipped in sulphate 



