THE HEART OF THE ANTARCTIC 



Whale-back Clouds. — The most striking of all the 

 cloud forms on Erebus were those to which we gave the 

 name of whale-backs. They were small patches of cloud, 

 isolated or two or three together, one over another, with 

 very evenly rounded upper surfaces, the lower surfaces 

 more indefinite, often rounded too. A very good develop- 

 ment of them occured on September 16, 1908. The largest 

 stratified group of them formed an object like a comet, 

 the others were isolated. This display went through many 

 changes, slowly and gradually. Two stages are figured. 

 The first figure shows the clouds at an early stage, in 

 which they appear imbricated in a characteristic manner, 

 observed on many other occasions They were then strati- 

 fied, showing generally three layers in each group. 



At a later stage, shown in the next figure, the whale- 

 backs were isolated, except the one large comet-like mass. 



While usually evenly rounded, the curves were fre- 

 quently reversed at the ends, as shown in the lower goup 

 in the first figure. 



Whale-backs were usually seen after a blizzard, occa- 

 sionally before one. During the blizzard the mountain 

 was generally hidden, so that we could not tell if they were 

 formed during the storm. 



Undulate Clouds. — Narrow lines of cloud were 

 often arranged in regular or irregular undulations. The 

 first figure shows fairly regular undulations, over the sum- 

 mit of Erebus, on July 28, 1908. The second figure 

 shows a modification of this form, in which the wisps of 

 cloud are intricately interlaced. This occurred on the 

 south side of Erebus, on September 16, at the same time 

 as well-developed whale-backs on the north side. 



Sometimes, especially after storms, a great variety of 

 clouds were piled up over and around Erebus, including 

 whale-backs, cumulus undulate clouds, with perhaps a 

 spiral cloud over all. 



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