Mr. W. R. Birt on a remarkable Baroinetric Depression. 19 



1806 to 1830 inclusive, on the 23rd, 24th, 25th, 26th and 

 27th of December. Tliese readings, which consist of the 

 maxima and minima, I have made the subject of a very care- 

 ful discussion, the result of which forms the subject of this 

 communication. 



Table L 



This table gives the principal features of the depression of 

 December 25, 1821, as it passed the neighbourhood of Lon- 

 don. As we proceed with the investigation we shall find 

 reason to isolate these observations. 



Table II. — Barometric Maxima and Minima on Dec. 25. 



From this table we learn that, with only two exceptions in 

 twenty-five years, the barometer attained an elevation of at 

 least 29-50 on the 25th of December in every year; the ex- 

 ceptions are the years 1810 and 1821 marked ^ and ''. 



Table III. 



C'J 



