﻿I. TIDAL OBSERVATIONS OF THE "DISCOVERY." 



BY 



SIR GEORGE DARWIN, K.C.B., F.R.S. 



The "Discovery" wintered in 1902 and in 1903 at the south-eastern extremity of Ross Island, on which 

 Mount Erebus is situated, in south latitude 78° 49' and east longitude 16G° 20'. 



The station is near the west coast of a great bay in the Antarctic Continent, and the westerly coast line 

 runs northward from the station for about 9° of latitude. To the eastward of the bay, however, the coast 

 only attains a latitude of about 75° and follows approximately a small circle of latitude. Since the tide- 

 wave comes from the east and travels to the west the station is not sheltered by the coast to the westward, 

 and the continent to the eastward can do but little to impede the full sweep of the tide-wave in the 

 Antarctic Ocean. It is true that Ross Island itself is partially to the east of the anchorage, but it is so 

 small that its influence cannot be important. Of course the westward coast line must exercise an influence 

 on the state of tidal oscillation, for regarding the tide-wave as a free wave coming in from the east, it is 

 clear that it will run up to the end of the bay and then wheel round northward along the westerly coast. 

 It would seem, then, that the situation is on the whole a good one for such observations. Of course their 

 value woidd have been much increased if it had been possiljle to obtain other observations elsewhere. 



The following account by Lieutenant MiCHAEL Barne, R.N., explains the manner in which the tidal 

 observations were made : — 



" On our arrival in the vicinity of our Winter Quarters on February 8, 1902, a good deal of the previous 

 year's ice remained attached to the land. As there was no foreshore, and pieces of this ice were constantly 

 moving out, it was impossible to erect a tide-pole. With the final departure of the old ice, the temperature 

 fell, and young ice formed continually, only to be quickly broken up by the almost incessant easterly 

 winds. 



" As this state of aftairs promised to last for a considerable time, an effort was made to obtain records 

 of the tides. A stout graduated pole was erected alongside the ice foot in about 10 feet of water, the 

 lower end being heavily weighted and the upper end securely guyed. Some intermittent observations 

 were secured in this manner, but they are probably of little value, as the ice was continually forming 

 round the pole, which was only with difficulty freed 

 from it. Besides this, communication with the shore, 

 and consequently approach to the tide-pole, was con- 

 stantly interrupted. 



"On the ship being finally frozen in, a tide gauge 

 of the following nature was erected (fig. 1). 



" A single length of pianoforte wire (sounding wire) 

 was led through a block, secured to the head of a 

 tripod. One end of this length was attached to 

 eight 25-lb. sinkers, which were lowered to the 

 bottom. Four 25-lb. sinkers were secured to the 

 other end in such a manner as to allow of their free 

 movement, between the ice and the block, as the ice, 

 with the tripod, rose and fell with the tide. An 

 indicator was clamped to the wire, and a suitable 

 scale secured to the tripod. Fig. 1. 



" It was thought that the motive force supplied 

 by the weight of four sinkers would be sufficient to draw the smooth surface of the wire through the ice as 

 the water rose and fell, whilst, in case it should fail to do so, the weight of eight sinkers would not be 

 sufficient to break the wire. 



B 2 



Indicator 

 4 25lb. sinkers 



