40 



DISCUSSION OF THE HORIZONTAL COMPONENT 



The values for 1843 within brackets are interpolated by means of the continued 

 readings at 14 b 21 | m ; at this hour the difference of reading from the preceding 

 year is 259, which added to the values of 1842 gave resulting normals for 1843; in 

 the same manner the reading in 1843 at 14 h 21 | m when compared with the reading 

 in the following year (1844) leaves the difference 185, which quantity when sub- 

 tracted from each hourly value in 1844 gives a second determination for the year 

 1843; the mean of the two determinations for each hour has been inserted above. 



