264 MR. J. BAXENDELL ON PERIODIC DISTURBANCES, ETC. 



results appears to be due to Dr. Dalton, who, at page i6 

 of the second edition of his Meteorological Essays, gives a 

 little table entitled " A table of the mean spaces described 

 by the mercury each month, determined by summing up 

 the several small spaces ascended and descended ; also the 

 mean number of changes from ascent to descent, and the 

 contrary, each month, it being reckoned a change when 

 the space described is upwards of '03 of an inch. The 

 means are for five years, at Kendal and Keswick." There 

 is no remark appended to this table, but in another part 

 of the work the author refers to it in support of his theory 

 of the variation of the barometer as showing that the 

 greatest disturbance of atmospheric pressure takes place 

 in the coldest period of the year, and having apparently 

 satisfied himself on this point it would seem that he never 

 afterwards resumed the subject, and it has since remained 

 almost entirely neglected by meteorologists. 



The two sets of numbers in Dr. Dalton's table indicate 

 a maximum of disturbance in the first week of January, 

 thus agreeing very closely with the results which I have 

 obtained for Dublin, Sandwich, and Greenwich. 



