439 



hypsometcr observations. At first two aneroids were in use, differentiated in the Register by the numbers 

 1 and 2, but the readings of No. 1 have not hero been used, as the error of the instrument was found to 

 have varied more than j$ of an inch between the date of issue and the 2nd November. No. 2 (Aneroid, 

 M.O. No. 2) agreed very nearly with the ship's standard mercury barometer at the beginning of 

 November, and the correction then obtained was in good agreement with the Kew correction, at 29 inches, 

 viz., - "02. After the 5th November the observations noted were of one aneroid only, and the instrument 

 is distinguished in the Register as H.O. 4 and M.O. 3. The mean correction for this aneroid was found to 

 be + '01 at 29 inches, when the returning sledge party was near to, or at, the ship from the 1st to the 

 3rd February, 1903, the error varying between - -01 and + '03. The correction, when issued, was + '02 

 at 29 inches ; it is fair, therefore, to consider + '02 as an approximate correction for this aneroid throughout 

 the journey. 



The results of the observations for pressure, to which the above corrections have been applied, are in 

 fair agreement with the results of the same observations corrected by applying the errors obtained from 

 time to time by comparisons of hypsometer observations with simultaneous reading of the aneroid. Both 

 are here given. 



As the height above sea-level was not known, it has been assumed that the area over which Captain 

 SCOTT and his party travelled was not much higher during the greater portion of the journey than the 

 height of the ice barrier at its edge, and in reducing the observations for pressure to mean sea-level a mean 

 altitude of 150 feet has been assumed. 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 gradual elevation 

 southward how much is an open question. 



In 'The Voyage of the "Discovery,"' Captain SCOTT states that on the 19th December "Everywhere 

 apparently there is a sharp and definite line between the land and the level surface of the barrier as exists 

 on an ordinary coastline between land and water." He was then in latitude 81 5' S., 162 6' E. 



If the barrier upon which the explorers were travelling did not rise with latitude to a much greater 

 altitude than that which has been assumed here as the mean altitude during the journey, then the increase 

 of pressure, with increase of latitude, confidently expected by former explorers of this quadrant of the 

 Antarctic, did not obtain. 



The results of observations show that the mean pressure to the south differed but little from the mean 

 pressure at Winter Quarters during the same periods. The differences between the two means are 

 curiously constant throughout, the average difference being about 0'05 inch, using the Kew correction, 

 and nil using the correction obtained by hypsometer observations. 



An increase in mean pressure between the first and second period of 0'37 inch is found at Winter 

 Quarters', against 0'34 inch on the sledge journey, using the Kew correction; and a diminution of mean 

 pressure between the second and third periods of 0'29 inch at Winter Quarters, against 0'24 inch on 

 the journey. Again, a diminution is shown between the third and fourth periods, which is only 

 0" 09 inch at Winter Quarters and 0' 14 inch on the journey. An increase of mean pressure is shown 

 between the fourth and fifth periods of - 14 inch at Winter Quarters, against 0'15 inch on the 

 journey, and a diminution between the fifth and sixth of - 27 inch at the former and of - 29 inch on 

 the latter. 



This similitude, in the rise and fall of mean pressure, between the Winter Quarters' pressure results on 

 the one hand, and the pressure results of observations made on the southern journey during the same 

 periods, suggests a mean distribution of pressure over the areas traversed to the eastward of the mountain 

 ranges, represented by an isobar running about N.N.E. and S.S.W. 



This supposition gains some confirmation by the fact that, during the journey to the south, the wind's 

 direction was mainly from south-south-westward. 



It siwms not improbable, indeed, that from Cape Adare to Mount Longstaff, and even still farther to the 

 south, the distribution of pressure conforms largely to the configuration of the high land, and that an area 

 of relatively high pressure lies over the land to the westward of the coast ranges, and relatively low over 

 the Ross Sea, giving gradients for southerly winds during the greater portion of the year. 



The tendency for the formation of a pressure gradient, with isobars along the coastline is generally 



