THE WEDDELL QUADRANT AND ADJACENT AREAS. 



133 



Additional Note, received 6th September 1908. 



Note on the Mean Monthly and Annual Barometric Pressure at Sandy 

 Point, the Falkland Islands, and in the Cape Horn Regions. 



The maps of mean monthly pressure given in this paper may he said to approxi- 

 mately represent the conditions prevailing during the five years 1903-1907. For this 

 reason the trend of the isobars over the ocean in the Cape Horn region as well as their 

 relative height will be found in some months to differ from those given in treatises 

 dealing with the results of maritime observations obtained from ships' logs extending 

 over long terms of years. With a view of giving good normals for land stations in this 

 region, I have made every effort to obtain values for Sandy Point, the Falkland Islands, 

 and for the Cape Horn area. For Cape Pembroke (Falkland Islands) the values of mean 

 monthly and annual pressure which follow are based on 16|- years' observations. For 

 the vicinity of Cape Horn, means deduced from observations taken at Staten Island, 

 Ushuaia, Harbertown, and New Year's Island are given. The periods embraced by the 

 records comprise 19 years for the months of February, March, and May, 20 years for 

 January, April, June, August, and December, 21 years for July and September, and 22 

 years for October and November. The monthly averages were obtained by taking the 

 mean of all or any of the above stations, observing simultaneously. Thus for the year 

 1905 the monthly means are the average of the mean pressures recorded at New Year's 

 Island, Ushuaia, and Harbertown. By this method a much closer approximation to the 

 true pressure was obtained than if the monthly means had depended on only one 

 station. The mean position of the stations is 54^ degrees south latitude, and 65 degrees 

 west longitude. Their range in latitude does not exceed a few miles, but in longitude 

 the stations differ some 4|- degrees or 160 miles. This variation in longitude is, how- 

 ever, unimportant, as the isobars in this locality normally approximate to parallels of 

 latitude. For Sandy Point the monthly means are based on 18 years' observations, so 

 that the values for all three districts are very nearly of the same length, although they 

 are not quite synchronous, being for different terms of years. In spite of this deficiency, 

 however, owing to the paucity of land observations in this part of the globe, they 

 afford the closest approximation that it is at present possible to obtain for the distribu- 

 tion of pressure at the south of the continent of South America, and over the ocean to 

 the east up to the longitudes of the Falklands in about 52° S. latitude. The follow- 

 ing table shows the mean monthly and annual pressure at the three stations. 



Mean Monthly Barometric Pressure at 32" Sea-Level and Standard Gravity. 



Station. 



Period. 



Years specified. 



Jan. 



Feb. 



Mar. 



Apr. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



29'520 

 •434 



•559 



Dec. Year. 



Sandy Point . 



Cape Horn ) 

 Region . j 



C. Pembroke or 

 Port Stanley 

 (Falklands) . 



18 years 

 19-22,, 



1 1871-72, 1889- \ 

 \ 1902, 1905-06 / 

 ( 1876-79, 1881-83, ) 

 1 1886-96, 1899, } 

 ( 1902-07 J 



/ 1859-68, 1875-77, \ 

 \ 1882-83. 1903-05 / 



29-485 

 ■&31 



481 



29473 

 -445 



■531 



•29-525 

 ■432 



■AM 



29-552 

 •502 



•539 



29-596 

 '495 



•538 



29-651 

 •551 



■606 



29-571 

 •527 



■576 



29-644 

 •570 



•549 



29650 

 ■625 



-644 



29-599 

 •538 



•623 



■438 

 •492 



29-559 

 ■499 



•551 



