XXXIV 



NOTES. 



called maxima to the west ; and that our " maxima to the east " (at 20 h and 

 10 h ) correspond to their minima to the west. In order to show the diurnal 

 march of the declination in the northern hemisphere, in its generality and ana- 

 logy, I take the denominations employed by Sabine ; and using the mean local 

 time of each place, and beginning with the greatest westerly elongation we 

 have : 



In particular seasons, Greenwich has shown some remarkable differences. In 

 1847 there was, in the winter, only one maximum (at 2 h ) and one minimum 

 (at 12 h ) ; in the summer there was a double progression, but the second mini- 

 mum occurred at 14 h instead of at 16 h (p. 236); the greatest westerly elonga- 

 tion remained attached to 2 h in summer as well as in winter. In 1846 (p. 94) the 

 secondary minimum was, in summer, as usual, at 20 b , but in winter at 12 b . 

 The mean winter increase to the west continued in this year, without interrup- 

 tion, from midnight to 2 h . Compare also 1845 (p. 5). Makerstoun (Rox- 

 burghshire in Scotland) is the observatory due to the munificent scientific zeal 

 of Sir Thomas Brisbane. (See J. A. Broun, Observations in Magnetism and 

 Meteorology, made at Makerstoun in 1843, p. 221 227.) On the hourly 

 day and night observations at St. Petersburg, see Kupffer, Compte rendu me'- 

 te'or. et magn. a M. de Brock en 1851, p. 17. Sabine points out, in reference 

 to his interesting and very sagaciously combined graphical representation of the 

 hourly declination curve of Toronto (Phil. Trans, for 1851, Pt. II. Plate 27), how, 

 previous to the small nocturnal movement to the west, which begins at ll h and 

 lasts till 15 h , there occurs a singular pause, lasting two hours, from 9 h to ll h . 

 " We find," Sabine remarks, " alternate progression and retrogression at Toronto 

 twice in the twenty-four hours. In two of the eight quarters (1841 and 1842) 

 the inferior degree of regularity during the night occasions the occurrence of a 

 triple max. and min.; in the remaining quarters the turning hours are the same 

 as those of the mean of the two years." (Obs. made at the Magn. and Meteor. 

 Observatory at Toronto in Canada, vol. i. p. xiv. xxiv. 183 191 and 228; 

 and Unusual Magn. Dist. Pt. I. p. vi.) 



For the very complete observations at Washington, see Gilliss, Magn. and 

 Met. Observations made at Washington, p. 325 (General Law). Compare there- 



