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XVI. " On the Lunar-diurnal Magnetic Variation at Toronto." 

 By Major-General EDWARD SABINE, R.A., D.C.L., Treas. 

 & V.P.R.S. Received June 13, 1856. 



(Abstract.) 



This paper contains the results of an investigation into the moon's 

 diurnal influence on the horizontal and vertical components of the 

 magnetic force at Toronto, and the consequent deduction of the lunar- 

 diurnal variations of the inclination and of the total force at that 

 station. The observations from which the results were obtained 

 consisted of five years of hourly observation of the bifilar and ver- 

 tical force magnetometer, ending June 30, 1848, from which the 

 disturbances of largest amount had been separated as described in a 

 paper previously communicated (Phil. Trans. 1856, Art. XV.). The 

 results derived from the mean of the five years are confirmed by 

 the accord which is shown of the means of each of the half-periods 

 into which the observations of the five years are divided for that 

 purpose. 



To complete the view of the moon's diurnal influence on the mag- 

 netic elements at Toronto, a recalculation has been made of the 

 lunar-diurnal variation of the declination from the mean of six years 

 of hourly observation, ending June 30, 1848, employing the more 

 perfect normals derived from the exclusion of the larger disturbances, 

 as described in the paper above referred to (Phil. Trans. Art. XV. 

 1856) ; and the confirmation is shown of the mean result of the six 

 years by the accordance of three separate portions of two years each, 

 into which the whole period of six years has been divided for that 

 purpose. 



From these premises the author draws the following conclusions : 



1 . The three magnetic elements concur in showing that the moon 

 exercises a sensible magnetic influence at the surface of the earth, 

 producing in every lunar day a variation which is distinctly appre- 

 ciable, in each of the three elements, by the instruments adopted and 

 recommended in the Report of the Committee of Physics of the 

 Royal Society, when due care is taken in conducting the observa- 

 tions, and suitable methods are employed in elaborating the results. 



