37H 



Results of Makerstoun Observations, 1844. 



TABLE XL. — Diurnal Range of the Vertical Component of Magnetic Force for each Civil Day, as 

 deduced from the Hourly Observations, with the Mean for each Week in 1844. 



Annual Variation of the Diurnal Ranges of the F'ertical Component. — -The following are the monthly 

 means of the diurnal range.s : — 



0-00 



Tlie diurnal range i.s a minimiun at the solstices and a maximum near the equinoxes. 

 When the means of tlie diurnal ranges are compared with the ranges of the mean diurnal variations (see 

 Table XLIII.), we obtain the following quantities, excesses of the former : — 



0-000 



so that the causes which render the mean diurnal range greater than the range of the mean diurnal variation 

 liave their minimum effect at the solstices, and their maximum in March and November. The same result has 

 been obtained for tlie horizontal component and magnetic declination. 



I 



