TRANSACTIONS OF SECTION E. 275 



tures of the air been also shown on the chart, in addition to 

 those of the water ; but, unfortunately, time does not permit tof 

 doing so in a satisfactory manner ; and it may be considered 

 that, although the question of fog in connection with ice is 

 interesting in many ways, it does not possess the importance 

 which the satisfactory solution of the question as to the best 

 route to Cape Horn assumes. It may be here stated that the 

 temperatures are taken by thermometers that have been tested 

 a.t Kew Observatory ; and to an ordinary observer it would 

 appear to show conclusively that at all seasons of the year, 

 and within certain limits irrespective of la,titude, there is 

 between the longitudes of 150° W. and 117° W. always a cold 

 ice-bearing current setting to the north-east ; and it may also 

 be noticed that, although more contracted in limits as far 

 as longitude is concerned during the austral winter months, 

 it is yet more clearly defined than during those of the summer, 

 though not carrying with it nearly as much ice. This can be 

 easily understood when one remembers that it is usually during 

 the early spring months that the great proportion of polar ice 

 breaks away from its moorings and sets out on its voyage, to 

 end in dissolution. 



As nearly as present information enables one to judge, the 

 breadth of this current varies from four or five hundred to 

 twelve hundred miles, the greater breadth being during the spring 

 and summer months. According to the data from which these 

 remarks are drawn — and they are thoroughly trustworthy — 

 this current cannot be overlooked even in the summer, not 

 because of the ice contained therein only, but also because of 

 its peculiar colour, which in two separate years was a dirty 

 ultramarine, and because it contained large quantities of sea- 

 weed and various kinds of floating matter. 



Of course, when it is attempted to frame a theory from 

 imperfect data, even in such a science as geology, it is neces- 

 sary to look round for collateral evidence sometimes, to prove 

 that of which one may feel perfectly convinced in one's own 

 mind. How much more truly will such a remark apply wdien 

 reasoning about an element that can hardly even be touched 

 with any instrument to serve in place of the geologist's ham- 

 mer ! but there is collateral evidence to be got even here. 



There can be no mistake in the recognition of an Antarctic 

 iceberg that has been recently broken from its birthplace ; for, 

 unlike the iceberg of the Northern Hemisphere, it is not a 

 detached piece of glacier-ice, but has always the characteristic 

 of being perfectly flat, or table-topped, and it is a somewhat 

 weird sight at times to see these enormous bergs, extending 

 perhaps two miles in length, with the top of this white wall 

 frequently dimmed by what appears to be mist rising from it. 

 This perfectly flat shape lasts until it has reached warmer 



