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XII. DISCUSSION OF THE OBSERVATIONS OF THE DIRECTION AND 



FORCE OF THE WIND AT WINTER QUARTERS AND ON 



THE SLEDGE JOURNEYS. 



BY 



R. H. CURTIS. 



THE STATION. 



THE immediate surroundings of any place at which observations of wind were made is a matter of some 

 importance when dealing with the observations themselves. The Winter Quarters of the "Discovery" were 

 in a small bight, about a third of a mile deep, close to the south-western extremity of Ross Island, where 

 the vessel lay east and west and fairly close to the shore. The neighbouring land was hilly, and extended 

 from Hut Point, a low promontory less than a quarter of a mile to the westward, round through north and 

 east to Observation Hill, a conical hill three-quarters of a mile to the south-south-east of the ship The 

 land, although hilly, did not rise very abruptly, and its highest point, which was much above the general 

 level, was reached at Crater Hill, 1000 feet above the sea and between one and two miles to the eastward 

 of the ship. Between this hill and Observation Hill there lay a wide gully, opening out to the south-east, 

 and known as the Gap. The outlook from the ship to the south-westward, from Observation Hill in the 

 south-south-east to Hut Point in the west was perfectly open and uninterrupted. 



An additional series of observations of wind direction and force was made at a point upon the open ice 

 about one-third of a mile to the south of Cape Armitage, the southernmost point of Ross Island. This spot 

 was about two miles south of the ship and, except for Ross Island, there was nothing that could obstruct 

 the wind coming from any direction. 



INSTRUMENTS. 



The instrumental equipment of the expedition for making observations of the direction and force of the 

 wind consisted of a non-registering vane of the ordinary type for observing the direction, and of three 

 anemometers for obtaining the velocity. In addition to the instrumental records, the force was also 

 estimated by the Beaufort scale. 



One of the anemometers was a small cup instrument, made by CASELI.A, which indicated upon a pair of 

 dials the number of miles of wind which had passed over it since the last observation. The cups of this 

 anemometer were 3 inches in diameter, and the distance from the centres of the cups to the spindle was 

 6| inches. Before leaving England it had been compared with the large anemometer at the Kew 

 Observatory, and within the limits of the wind velocities experienced during the time the trial lasted the 

 indications of both instruments were found to be in fairly close agreement. The results shown by the 

 larger instrument are, however, known to be too high, and have to be reduced in the ratio of 15 to 11 to 

 obtain the true speed of the wind, and therefore the dial readings of the smaller instrument were all 

 similarly reduced before they were dealt with in this discussion. 



This cup anemometer was mounted upon an iron post, which was fastened to the wooden frame erected 

 to carry the thermometer screens. The cups were 15 feet above the level of the snow and about 120 yards 

 to the eastward of the ship. 



The dials were read every two hours when making the other meteorological observations. The readings 

 have been first corrected for the factor, as indicated above, and then divided by 2 in order to get the 

 average hourly speed of the wind in statute miles since the last observation. 



Both the other anemometers were pressure-tube instruments, but of different patterns, one being a self- 

 recording instrument, made by MUNRO, and the other a non-recording, or " sight-indicating," instrument 

 by CAKELLA. 



The latter is a small portable instrument, not intended to be permanently fixed, but to be held in the 

 hand when making an observation. In the present case, however, it was attached to another upright of 

 the stand to which the thermometer screens were fixed, and was connected by tubes with a duplicate vane 



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