257 



XX. — On a System of Periddic Disturbances of Atmo- 

 spheric Pressure in Europe and Northern Asia. 

 By Joseph Baxendell, F.R.A.S. 



Kead November i3tli, i860. 



In the course of an investigation of the phenomena of 

 the general disturbances of the atmosphere which I made 

 some time ago^ I was led to conclude that moderately 

 accurate determinations of the sums of the irregular 

 oscillations of the barometer for given periods, at different 

 places on the surface of the earth, would afford valuable 

 information respecting the nature of these disturbances, 

 and at the same time throw additional light upon the 

 causes by which they are produced. It is obvious that 

 even the most accurate determinations of the statical 

 element of mean pressure can be of only very limited use 

 in an inquiry of this kind; but notwithstanding the im- 

 portance of the subject, meteorologists have generally 

 neglected to ascertain even approximately the values of 

 the dynamical element as represented by the extent and 

 frequency of the oscillations of the mercurial column. In 

 none of the many volumes of observations which issue 

 from the public observatories of this country and the con- 

 tinent have I yet seen any attempt made to deduce the 

 values of this element. In the Greenwich, and also in 

 some of the Oxford volumes, tables of the principal max- 

 imum and minimum readings of the barometer are given, 



SER. III. VOL. I. LL 



