114 MONTHLY ABSOLUTE VALUES OF THE 



MONTHLY ABSOLUTE VALUES OF THE MAGNETIC 

 ELEMENTS AT TORONTO, FROM 1856 TO 1864, INCLU- 

 SIVE. 



BY G. T. KINGSTON, M. A., 



DIEECTOE OF THE MAGNETIC OBSEEVATOET. 



Declination. — The monthly values given in table L, are the 

 means of six separate determinations, made at intervals during two or 

 three consecutive days. Each determination includes five readings of 

 the collimator scale, accompanied by simultaneous readings of the 

 differential declinometer, by aid of which the corresponding partial 

 determination was reduced to the monthly twenty-four-hour mean 

 normal reading of the differential declinometer. 



The mean monthly increase of westerly declination, derived by the 

 method of least squares, from the 108 equations furnished by the 

 monthly values of declination, is 0'*2606 ; which, if the rate of west- 

 erly movement increase equably, will be the monthly rate correspond- 

 ing to 1st July, 1860. But on p. vi. of Vol. II. of the Torontcr 

 Observations, the monthly rate of westerly movement proper to 1st 

 July, 1848, was 0'*1627 : whence the mean annual increase in the 

 monthly movement is 0' 008 nearly. The probable error of a single 

 monthly determination is 0'"74, and the probable error of the mean 

 determination, 2'^ 10''04, corresponding to 1st July, 1860, is 0'-071. 



Table II. gives the monthly determinations of the dip, and Table 

 III. those of the horizontal force, taken according to the method of 

 which the details are given in the earlier volumes of the Toronto 

 Observations. The determinations of the horizontal force are reduced 

 to the monthly twenty-four-hour mean normal reading of the bifilar. 



The monthly values {<f) of the total force in Table IV. are derived 

 from those of the dip (0) and of the horizontal force (X), by the 

 formula <^=X sec. 6. 



For the purpose of exhibiting the progressive secular march in the 

 magnetical elements from the commencement of the observations, the 

 annual means, as far as they are procurable, are presented in on? view 

 in Table V. 



Declination. — The annual means of the declination for 1841-42 

 are taken from p. xi. of Vol. I. of the Toronto Observations, and those 

 for 1845 to 1851, from pp. iii. to v. of Vol. II. In 1853, 54, 55^ 



