40 



Mr. J. A. Broun on Simultaneous 



[May 11, 



same time the great similarity which has presented itself between the 

 movements at St. Helena and at the Indian stations during the week 

 March 31 to April 5, 1845, induced me to make a comparison for that 

 week with the barometric movements at the Cape of Grood Hope, nearly 

 in the same longitude as St. Helena. 



The results of this comparison were so important that observations at 

 other stations were also examined. 



The geographical coordinates of the different stations considered are 

 as follow : — 



Stations. 



Latitude. 



Longitude 

 from Grreenwich. 



Height above 

 Sea. 







h m 



feet. 



1. Hobarton 



42° 52 S. 



9 50 E. 



105 ^ 



2. Pekin 



39 54 N. 



7 46 E. 



Eew t 



3. Cape of Good Hope . . . 



33 56 S. 



1 14 E. 





4. St. Helena 



15 57 S. 



23 W- 



1764 ^ 





55 35 N. 



10 W- 



213 \ 





1 19 N. 



7 16 E. 



Few § 



7. Madras 



13 4N. 



5 21 E. 



30 § 





31 6 N. 



5 9 E. 



7096 § 





56 50 N. 



4 2E. 



1000 ? t 





59 45 N. 



4 OE. 



1400 ? t 



The observations made at these stations during the week March 3 1 

 to April 5 were discussed in the same manner as before, so as to obtain 

 the daily means corresponding to each hour or two hours ||. 



The daily means thus obtained are projected, Plate 1. Since the 

 daily movements were found much smaller within the tropics than in 

 high latitudes, the curves are projected on different scales to make the 

 variations equally distinct •[[. The following are the principal conclusions 

 from these projections. 



All the curves show a maximum near the beginning and another near 

 the end of the week, with a minimum near the middle. The turning- 

 points occur in the following order at the different stations : — 



* 1, 3, 4. Observations made at the Mag. and Met. Obs. at Hobarton in Van Diemen 

 Island, at the Cape of Grood Hope, and at St. Helena, printed under the superinten- 

 dence of Colonel E. Sabine. 



t 2, 9, 10. Annuaire Mag. et Met. publiees par A. T. Kupffer, Annee 1845. 



I 5. Observations in Mag. and Met. Edited by John Allan Broun. Trans. Roy. 

 See. Edin. vol. xix. 



§ Previously cited. 



II At Pekin the observations were made two-hourly from 5"^ a.m. to 9^* p.m., and the 

 barometric heights for ll'* p.m., and P and 3** a.m. were found by interpolation for 

 this discussion : similarly for Bogoslowsk, where observations were made from 8** a.m . 

 to 10*^ P.M., the heights for the even hours from midnight to 6*^ a.m. were obtained by 

 interpolation. 



^ It should again be remarked that the hours at the head of the vertical lines are 

 the local hours for each station: the vertical line corresponding to 12^ April 2^, 

 Grreenwich mean time, is marked with an asterisk for each curve. 



