December 17, 1908] 



A^A TURE 



203 



\riv pcrnu-able to solar radiations, and that lliis is due 

 to the small amount of aqueous vapour present. 



During' the two j'ears under discusison no rain fell on 

 Ross Island. The measures of snowfall are somewhat 

 doubtful, and were obtained by driving stakes into the 

 snow and measuring at intervals the length exposed. The 

 only point that is definite is that the total fall for the two 

 years must have been very small. 



Observations on the amount of evaporation were made 

 during the winter by weighing small dishes of ice daily, 

 the ice having been formed in the dish so that the surface 

 was smooth and measurable. Notwithstanding the very 

 low temperatures of the winter months, the evaporation 

 was very great, the mean monthly value being 0-25 inch, 

 which is almost double that for the winter months in 

 London, where the temperature is nearly 50° higher. 

 These observations confirm the opinion expressed as to the 

 low humidity indicated by the wet- and dry-bulb thermo- 

 meter readings. 



The observations on wind direction, when reduced to 



eight points, show 8 per cent, of north winds, 5 per 



cent, of south winds, 61 per cent, between north and south 



M the east side, and 3 per cent, on the west side; 23 per 



111. of the observations recorded " calms." The observa- 



1 * . "; J-. 'ijiittt 



^ , , -'^fc ". \ ,. . '".'' i^T^ff, . . ?yl'"' . 



-U-i^WJiHt'. >-J■ ° P^^ 



t jy it w, i_iM - i-gtM-v\-ai;v 



-rrf,,...i, .■.:,t^..',"^ 



RmtjvaaaMBi\aai 



e|-a.\ja\;r#rVa\¥ 



:;. 2. — Reproductions of traces of the self-recording instruments at winter quarters, representing 

 rapid fluctuations of temperature and an associated barometric trace, (i) Thermograph record 

 of temperatures between - 50' K. and 5° F., fune 22 to 28, 1903. (2) Barograph record for com- 

 parison showing the absence of any noteworthy change of pressure to correspond with changes of 

 temperature. 



tions at Cape Armilage, 3000 yards awav, agree with 

 this. 



On the sledge journey made by Lieut. Royds and party 

 to the south-east, across the Great Ice Barrier, observa- 

 tions of wind direction were made, but the rough note- 

 book does not say whether the directions entered are 

 "true" or "magnetic." Lieut. Royds afterwards wrote 

 that they are " true " bearings, and indicate south-west 

 winds. In the discussion by Mr. Curtis they are treated 

 as doubtful, and as possibly easterly winds. The records 

 (if other sledge journeys often show southerly or south- 

 w'sterly winds. 



The direction of movement of lower clouds was in 

 47 per cent, cases between south-east and south-west ; of 

 Mount Erebus smoke, 76 per cent, cases between south 

 nnd west ; of upper clouds, 64 per cent, cases between 



■ iirh-west and north-west. 

 The mean barometric pressure during the period 

 t ' Ijruary, ic)02, to January, 1904, was 2q-2Q inches, and 

 comparing this with the observations made on other ex- 

 peditions, and bearing in mind the prevalence of easterly 

 winds at the ship's station, it is deduced that the baro- 

 metric pressure should be relatively higher over the regions 

 towards the Pole. 



In this connection the observations made on the various 

 sledge journeys become important, though in the dis- 



NO. 2042, VOL. 70] 



cussions of them .\Ir. Curtis and Commander Hepworth 

 reach diffi'ient conclusions. 



Mr. Curtis, discussing the observations of pressure made 

 by Lieut. Royds on his journey across the Barrier in 

 November, 1903, plotted them oji a distance scale, read- 

 ing to and from the ship, and apart from the general 

 fall on the outward journey and the rise on returning, 

 recognises points which seem to indicate fairly definitely 

 changes in altitude. The reading taken at the furthest 

 point of the journey (170 miles) was about 0-25 inch lower 

 than that taken on the ship at the same time. If this 

 gradient was real, then the winds experienced on the 

 journey should have been stronger than were recorded. 

 If the gradient was not real, then the difference was most 

 probably due to change of altitude. Assuming a rise of 

 2 feet per mile (an amount apparently warranted by the 

 evidence of ice pressure and the northerly movement of 

 the ice barrier), and reducing the barometer readings 

 accordingly, the pressure at the last station on the journey 

 would then be read as one-tenth of an inch greater than 

 at the ship. Mr. Curtis concludes, therefore, that the 

 pressure rises to the south. 



Commander Hepworth, in his memoir on the climatology 

 of South Victoria Land, makes a long and careful com- 

 parison of the observations made by 

 all the Antarctic expeditions and on 

 excursions from Ross Island. Atten- 

 tion is often directed to pronounced 

 differences between the weather ex- 

 perienced by the sledge parties and 

 that prevailing at the Discovery. 

 Wind, temperature, and pressure all 

 differ, and Commander Hepworth finds 

 ■iufficicnt justification for accepting 

 Lieut. Royds's statement that the 

 inds on his journey across the 

 1 larrier were south-westerly. 



Captain Scott in his book, " The 

 N'oyage of the Discovery," says, of 

 another excursion, " on comparing 

 notes with this party we realised for 

 the first time what a difference there 

 might be in the weather conditions 

 within easy reach of the ship. It was 

 not only in the inatter of tempera- 

 ture — as I have already described — but 

 ilso in the force and direction of the 

 wind. . . . Already we had learnt 

 that the prevalent wind at our winter 

 quarters blew from the south-east 

 through the Gap, and that this wind 

 was usuallv local and frequently 

 ceased within a mile or two from the 

 ship." 



Commander Hepworth says that in 

 correcting the observations of pressure made on sledge 

 journeys he has assumed a mean altitude, whilst " it is 

 recognised at the same time that the assumption of a 

 mean altitude is scarcely admissible, as the whole 

 mechanism of ice distribution implies some gradu.al eleva- 

 tion southwards — how much is an open question." 



Bv this method of correction " the results show that the 

 mean pressure to the south differs but little from the mean 

 pressure at the winter quarters." 



" It seems not improbable that indeed from Cape Adare 

 to Mount Longsfaff and even still further to the south, the 

 distribution of pressure conforms largely to the configura- 

 tion of the high land, and that an area of relatively high 

 pressure lies over the land to the westward of the roast 

 ranges and relatively low over the Ross Sea, giving 

 gradients for southerly winds during the greater portion 

 of the year." 



The 'existence of the Antarctic anticyclone is not yet 

 proved, though many facts point towards it. 



Some of the differences between the results arrived at 

 by those who have discussed the observations are cer- 

 tainly due, to some extent, to imperfections, some of them 

 inevitable, in the observations themselves, but it seems 

 probable that if the statements made by certain members 

 of the expedition had been accepted, as thev should have 

 been, some of these differences might have disappe.are'"- 



M. 



