478 



NATURE 



{March 18, 1880 



conform to the sun-spot period, one or two facts have already 

 been noticed in the pages of Nature by Mr. F. Chambers 

 (vol. xviii. p. 567), and Mr. Archibald ' (vol. xx. p. 28) ; but 

 those which I have now to bring forward will serve to give it 

 greater precision, and a much more extended basis, and they 

 serve also to throw some slight additional light on the nature of 

 the agency by which the oscillation is effected, and which has, I 

 think, been misapprehended by one if not both of the above 



writers. In the present communication I shall restrict myself to 

 this subject, reserving the more abstruse question of the anomalous 

 element for future discussion. 



To begin with the most regular and uniform case of variation, 

 that of an insular station situated almost on the equator. The 

 barometric register of Singapore in lat. 2° (elevation 10 feet above 

 sea-level) gives the following deviations from the several monthly 

 averages since its commencement in 1869. 



I must observe that in 1869 and 1S70 the register was taken 

 from the readings of a different barometer from that used subse- 

 quently, and no comparison has ever been made between them. 

 There may thus be some small uneliminated error in the figures 

 for these two years, but since both Batavia to the south and Port 

 Blair to the north show a barometric depression in 1870 not less 

 persistent and (in the case of Port Blair) almost as intense, this 

 error can hardly be of importance. The registers of these two 



latter stations show the following differences. For that of 

 Batavia, I am indebted to the kindness of Dr. Bergsma, 

 who has communicated to me a proof sheet of his forth- 

 coming volume. The values are in millimetres. The Port 

 Blair table is drawn up from the registers ill the Calcutta 

 Meteorological Office, reduced to the Calcutta standard and 

 the present elevation of the barometer at 6l"l6 feet above half- 

 tide level. 



Batavia (millimetres). 



Port Blair (English inches 



The registers of Colombo also (N. lat. 6° 56') as far as they 

 go, viz., since 1872, show a similar graduated variation, but those 

 of the Mauritius, for which I am indebted to the kindness of Mr. 

 Meldrum, differ considerably, and indicate a pressure below the 



* Mr. Archibald mentions that the relation discussed was brought to his 

 notice by Mr. S. A. Hill. 



average in 1867 and 1S6S, and above it in 1S71. In 1S76 and 

 1S77, however, they agree with those of the other stations in 

 showing an unusually high pressure. The following table shows 

 the annual deviation of the mean pressure at each of the five 

 stations since the commencement of the registers, all being 

 reduced to English inches. 



