Meteorology. — "On the irJatlou hetuKen mefeorolot/ical coiulitlons 

 ill till' Ni'tlii'rhiiids iiiiil some circwnjacevt places. Atinospheric 

 Pressure." By Dr. J. P. van der Stok. 



(Communicated in the meeting of May 29, 1915). 



J. K'or the knowledge of tlie climate of a country as also for 

 the forecasting of the weather, it is of importance to investigate in 

 how far a relation exists between the meteorological conditions 

 within a limited region and in circumjacent places, chosen for this 

 purpose, and to what degree local influences are felt. 



Statistical methods, leading to empirical, numerical relations, 

 involve the objection that many peculiarities, especially secondar}' 

 phenomena, disappear by the collective treatment, but by their means 

 existing relations may become more prominent, which necessarily 

 remain unobserved by those who, for many years, have made a 

 special study of the individual phenomena and, if no new relations 

 are brought to light, quantitative rules are substituted for qualitative 

 knowledge. As the most simple and prijicipal problem, the question 

 will be examined, what relation exists between the oscillations of the 

 atmospheric pressure at de Bilt and the oscillations at a few surround- 

 ing places. 



The isobars for different months and the corresponding average 

 values of the wind show that this relation can hardly be the same 

 in different seasons. We come to the same conclusion by investigating 

 the relation existing between barometric oscillations within the region 

 of high pressure near the Azores and of low pressure near Iceland, 

 by which the climate of Western Europe is considerably affected. 



Each factor indicates that the observations made during the months 

 of January, February, and December are the fittest material for this 

 inquiry which, therefore, is restiicted to the wintermonths. 



2. The method followed is simple, but necessarily laborious. 



If the deviations from the average barometric height at a central 

 point and the circumjacent stations be denoted by c,, .r^ ...,*:„, then, 

 the quantities under consideration being small, a linear relation may 

 be assumed to exist 



.y, = ^,,.«3 + ój,.r, /)i,,).'„ = F, , . . . . (1) 



and the coefficients h can be calculated by means of the metiiod of 

 least squares from the n — 1 equations formed by multiplying the 

 equations (1) successively by d\,x^...,r,n and addition of the total 

 numbei' of equations. 



