4 T. V. HODGSON. 



water never came within five miles of the ' Discovery,' so that in the following season 

 its gradual approach was watched with more than ordinary interest, not to say 

 anxiety. On January 4th, 1904, when the relief ships arrived there were at least 

 eighteen miles of ice still to go ; some fourteen miles went out in about six weeks, 

 but on February 14th the necessary conditions obtained, and four miles of fast 

 ice broke up and started northwards in about as many hours. At the time it 

 was practically a dead calm, so that the wind had no influence. When we 

 passed Winter Harbour for the last time, on February 18th, the last masses of 

 ice were floating out, a phenomenon which had occurred one day earlier two years 

 previously. 



The foregoing is the briefest possible account of the ice conditions prevailing 

 in McMurdo Sound, and is not without biological interest, as by it the Sound may 

 be divided into three areas. 



The first, or Northern area, extends from Cape Bird to the so-called " glacier 

 tongue," and includes the Dellbridge Islands. This is on the eastern side of the 

 Sound. A line drawn from the " Glacier Snout " to the southern boundary of New 

 Harbour forms the southern limit of this area. Open water occurs in this area for 

 at least four months of the year as a general rule ; in the more northern part of the 

 area, beyond Cape Royds, the period of open water is probably much longer. This 

 is incontestably proved by the Penguin rookery at Cape Royds and the large 

 breeding place for the Skua at Skuary Point, neither of these species going far from 

 water except in occasional wanderings. The Penguin requires open water and a 

 convenient landing place, both of which were obtainable at Cape Royds ; the Skua 

 is less dependent on either, but seeks for the former. Our presence brought immense 

 numbers to Hut Point, but only a few stragglers bred there ; they bred in very 

 large numbers on the numerous islets on both sides the Sound, where the open water 

 was within easy reach. 



The second, or Central area, includes the rest of the Sound south of the Glacier 

 Tongue and New Harbour, which is periodically open to navigation, Tarely exceeding 

 a couple of months at this point, a good deal less than that south of Cape Armitage. 

 A small area of open water occurred under Hut Point during the summer, caused 

 mainly by the ice-movements in the vicinity. A large lake also appeared off 

 Cape Armitage, over a shoal, and was fully half a square mile in area. The 

 explanation of this phenomenon ultimately arrived at was that the shoal brought 

 the deeper and warmer .waters of the Sound to the surface as the current swept 

 past the Cape, and so melted the ice through. This occurred in January 1902 and 

 1903, and a little later in 1904. It had just frozen over when we arrived in 1902. 



The third, or Southern area, is much the largest, and includes the whole of that 

 part occupied by the permanent or barrier ice. As the ice is covered as soon as it is 

 formed by a thick deposit of salt crystals and very shortly afterwards by snow, it 

 forms an opaque covering over the sea bottom through which no light can penetrate, 



