1867.] 



On the Barographs at Oxford and at Kew. 



413 



imponderability ; it will then be competent to fulfil its divine mission of 

 transmitting light and heat, without doing any violence to some of the 

 most fundamental notions of dynamics ; and thus imponderability may 

 cease to be reckoned amongst the physical attributes of matter. 



March 28, 1867. 

 Lieut.-General SABINE, President, in the Chair. 



The following communications were read : — 



1. "A Comparison between some of the simultaneous Records of 

 the Barographs at Oxford and at Kew." By Balfour Stewart, 

 LL.D., F.R.S., Superintendent of the Kew Observatory. Re- 

 ceived March 4, 1867. 



Through the kindness of the Rev. Robert Main, director of the Rad- 

 clifFe Observatory, Oxford, certain marked features of the curves produced 

 by the barographs at Oxford and at Kew were compared together on four 

 separate occasions in the year 1863. 



These comparisons are the more interesting that they were all made 

 during squalls or storms ; for on such occasions it is found that the baro- 

 graph curves exhibiting the height of the barometer from moment to 

 moment present curious characteristic points, without which indeed no 

 such comparisons could be made. 



The result for these four occasions in 1863 was as follows : — 



Nature of disturbance. ^^OxforcL ' ^' Kew 



Sudden increase of pressure 

 during squall of 30th Oc- 

 tober 1863 2.30 P.M. 3.9 p.m.? 39 minutes 



Sudden increase of pressure (probably), 

 during squall of 21st No- 

 vember 1863 4.0 p.m. 4.4.5 p.m. 45 minutes. 



Peculiar points in the curves 



of December 3, 1863 (a 2.40 a.m. 3.35 a.m. 55 minutes, 



stormy day) 6.50 a.m. 7.40 a.m. 50 minutes. 



Mr. Main has kindly called my attention to a well-marked minimum in 

 the Oxford curve for February 6, 1867, which was also a stormy day. 

 This minimum occurred at Oxford at 2.20 a.m. of that day, while at Kew 

 it did not occur until 3.15 a.m. Oxford was thus on this occasion 55 

 minutes before Kew. 



The peculiarity of this last occasion is the singular likeness between the 

 two curves. I have not compared together any other features of these 

 curves, nor perhaps could this be done with exactness ; but the general 



VOL. XV. 2 M 



