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Miss Cave-Browne-Cave and Prof. K. Pearson. [June 3. 



Atlantic stations, and this has impressed us with the desirability of 

 continuing, if possible, our chain of stations right down the west 

 coast of Africa, even to the Cape. The great mass of material to be 

 dealt with, and the many new problems which arise in an almost entirely 

 novel investigation of this kind, have meant of course very slow 

 progress, and while publication of the final conclusions must be delayed 

 for some time yet, it seems desirable to draw attention to some of the 

 results already reached for the East Atlantic stations. 



(4.) In the first place it was soon discovered that the winter and 

 summer months (equinox to equinox) must be treated separately. It 

 was already known that the average height varied considerably in 

 the summer and winter months, but there are also very significant 

 differences in the variability, and, in what we are most concerned with, 

 the correlation. For example, there is hardly any correlation (0*04) 

 between Lisbon and Valencia in the summer, but in the winter it is 

 quite considerable (0*22). Further, the results worked out in two 

 groups of 10 years each, show that very sensible differences in mean, 

 variation, and correlation can exist between one decade and the next r 

 so that at least 20 and probably more years are desirable if we 

 are to obtain steady values for the barometric constants. In the 

 next place while we have found a small but sensible cross Atlantic 

 barometric correlation after a definite interval of time, we must wait 

 for more complete American data, and for still closer investigation of 

 the best interval for different stations before results on this point are 

 published. The second suggestion, however, has been amply verified, 

 and to draw attention to this is the principal object of the present 

 preliminary notice. 



As we go generally south from any station, we reach a point at 

 which for readings on the same day there is no correlation at all. For 

 stations beyond this 'point the correlation becomes negative, reaches a negative 

 maximum, and then begins to decrease. Clearly it must reach a second 

 zero. What happens after this 1 Does the correlation remain zero for 

 all greater distances ? To fully answer this problem we must obtain 

 data south of Sierra Leone — in fact, we want data for St. Helena's, 

 Ascension, and the Cape, and have taken steps to obtain them. But 

 our confident belief is that the negative zone will be found to be 

 followed lyy another zone of positive correlation, but of far less 

 intensity. In fact, starting with any northern station and going south 

 across the equator, we expect to reach alternate zones of positive and 

 negative correlation, each zone marked by a successively smaller 

 maximum. These zones are not peculiar to the earth, but rather to 

 the station from which we start. 



Thus Valencia is positively correlated with B#d0. Lisbon, however, 

 is negatively correlated with B0CI0, but positively with Valencia. We 

 require to go as far south as Funchal to find a negative correlation 



