566 



The question of areas of barometric pressure or lines (which Espy 

 contends for), namely, long lines from north to south, or from one 

 point direct to another, having been much discussed, the principal 

 object of making the sections, as it were soundings, of the atmo- 

 sphere which are shown in the diagrams, was to prove whether lines of 

 pressure, or whether areas of pressure prevailed ; and in the author's 

 opinion, when they are closely examined they go to prove that while 

 the atmosphere in the British Islands varies in its pressure from time 

 to time, such variation is not along a particular line, but extended 

 over a large and wide area. 



As remarkable exceptions to the force of these particular storms, 

 it may be noted that at some places there was little or no wind ; 

 although the barometer fell much, without any consequence but rain. 

 The wind circulating around these districts did not affect them, while 

 at other places the storm was tremendous. 



The following few details are given respecting the data on which 

 the diagrams have been constructed : 



The probable limits of error of the barometric curves on the synoptic 

 charts, 2\st October to 2nd November, 1859. 



1. Observations quite correct. The observations at the regular 

 observatories, such as Greenwich, Oxford, Cambridge, Wrottesley, 

 Highfield House, Kew, &c., have had all corrections applied, and 

 have been reduced to sea-level, and the temperature of 32 Fahr- 

 enheit. 



2. Error probably very small, less certainly than half a tenth. 

 The returns from members of the British and Scottish Meteorological 

 Society (nearly ninety in number) have been corrected for height 

 above sea-level, within a few feet ; and the corrections of instru- 

 mental errors with reductions to 32 have been applied. 



Observations probably within a few hundredths of an inch. The 

 continental observations, collected from Dutch papers and from the 

 " Moniteur," have been reduced to 32, and have also been corrected 

 for instrumental errors. 



The heights of some stations are known, and the corrections due 

 to those heights have been applied, while others are but little, if at 

 all, above the sea-level. 



