1902.] 



Correlation heticeen Barometric Heights. 



467 



with Valencia. To get a negative correlation with Lisbon we must 

 go as far as Sierra Leone, which has become positive again for both 

 B0d0 and Valencia. At St. Helena's we have our second negative 

 correlation zone for both Bjzdp and Valencia, while we are only in the 

 second positive zone for Lisbon. In other words, the curve of baro- 

 metric correlation with distance from a station appears to give roughly 

 the form : — 



X 



We do not find with increasing distance a diminishing correlation, 

 as of a curve rapidly asymptoting to o x, but as it were a wave-curve 

 of diminishing amplitude. There is not apparently an area of positive 

 correlation surrounded by a field of zero correlation, but going south 

 there are only points of zero correlation, not regions of zero correlation. 

 Probably if the area of investigation can be extended we shall find 

 lines not zones of zero correlation round each station, separating 

 districts of positive and negative correlation. 



Now the results which we have copied for Sierra Leone and St. 

 Helena's are not at present complete enough to enable us to be 

 absolutely definite with regard to them. In particular, Skudesnaes 

 and Sierra Leone appear to give a discordant result. But our object 

 in the present note is merely a preliminary one. We wish to call 

 atteation to a rather remarkable relation between the barometric 

 height of stations at increasing distance, and by so doing emphasise 

 the importance of complete returns for stations in the southern 

 hemisphere. 



(5.) The following will illustrate our point : — 



Table I. 



Station. 



Bodo. Skudesnaes. 



Yalencia. 



Lisbon. 



Remarks. 





1 -6905 

 0-6905 j 1 

 0-0940 1 0-4631 

 -0-2815 -0-1606 

 -0-1881 -0-2305 

 + 0-0079 [-0-0505?] 

 -0-0841 -0-0231 



-0940 

 -4631 

 1 



-1547 

 - -0723 

 + -0188 

 -0 -0224 



-0-2815 

 -0-1606 

 -1547 

 1 



-7429 

 -0-0495 

 + 0-0135 



20 years. 

 j> 



10 years. 

 6 years 

 (winter only) . 



Skudesnaes 

 Valencia . . 

 Lisbon .... 

 Funchal . . 

 Sierra Leone 

 St. Helena . 



The results for the first five stations are based on far more reliable 

 material than those for the last two. But the latter suffice to suggest 



