Barometric Wave, November ISt?. 43 



horizontal line in this figure just touches the first interior 

 minimum value 30*1 98, difF. 'lOl. The same lines in fig. 2 

 are respectively 30'1 15 and 30 062, difF. -053, and in fig. 3 

 29-650 and 29'600, diff. -050: it is likely the triie difference 

 was less. The above numbers relative to fig. 3 are those 

 taken from the curve of 1798. It is to be remarked that the 

 second interior mininmm in that year was the lowest. The 

 principal difference between the curves of 1798 and 1847 

 consists in the greater elevation of the central portion of the 

 curve of 1798. The curve of 1846 appears to exhibit the 

 greatest deviation from symmetry. 



The preceding remarks refer more particularly to the /V^se 

 presented by the curve in any given locality, and also to the 

 devialiotis in certain directions from a well-recognised tijpe, 

 embodying the essential characteristics of the curve during a 

 definite period ; and although this period is variable within 

 certain limits, yet the similarity of the curves (such similarity 

 consisting, as before noticed, in a peculiarity of character, by 

 which the individuality of the curve is readily recognised) 

 appears to be confirmatory of the idea suggested by the ob- 

 servations of 1845, namely, that we have obtained the type of 

 the barometric oscillations during themiddle portion oj' November. 

 The occurrence of the curve in the year 1798, its appearance 

 at Dublin in twelve out of seventeen years' observations be- 

 tween 1829 and 1845, together with the regularity of its return 

 at London from 1841 to 1847, must certainly place this matter 

 beyond a mere hope, as expressed in 1845, and lead to the 

 conviction that a careful study of these curves will enable us 

 to make out some of their luvos. At all events, the attentive 

 meteorological observer has already been so far successful as 

 to recognise the last in its earliest stage, confirming, to a cer- 

 tain extent, the view of Sir John Herschel, expressed in his 

 Report on Meteorological Reductions*, 1843. " And it would 

 be no small meteorological discovery, if, by the study of the 

 character and progress of barometrical fluctuations, we could 

 either make out any law of the greater ones which would 

 enable us even roughly to predict them, or any peculiarity in 

 their physiognomy by which we could recognise them in their 

 earlier stages, as by this we might possibly be led to the pre- 

 diction of great storms." 



This remark of Sir John's clearly indicates the two direc- 

 tions in which this interesting study is to be prosecuted, — the 

 characters oi \.\\e barometric fluctuations and also their pro- 

 gress. The reader will find each of these branches amplified 



• Reports of the British Association for the Advancement of Science, 

 184.3, p. 99. 



