Prof. Norton on Molecular Physics. 



207 



mean value is 11' 15 years. He gives a formula for determining 

 the spot- condition of the sun at different dates, in which the seve- 

 ral terms represent the specific actions of the four planets just 

 mentioned, dependent upon their masses, distances, and annual 

 motions, and which gives results in close correspondence with the 

 results of the observations made between 1826 and 1848 (Astro- 

 nomische Nachrichten, No 1181). He has more recently extended 

 his investigations so as to include, but with less certainty, a much 

 longer period. 



The epochs of maxima and minima from 1750 to 1856 are 

 given in the following Table, to which we have added the corre- 

 sponding mean heliocentric longitudes of Jupiter and Saturn, 

 the two planets upon which the varying number of spots deve- 

 loped during a year chiefly depend. 



Epochs of 

 maxima. 



Jupiter. 



Saturn. 



Epochs of 

 minima. 



Jupiter. 



Saturn. 





o 



o 





o 



o 



1750-0 



4-42 



231-6 



1755-7 



1774 



301-4 



1761-5 



353-4 



12-2 



1766-5 



145-1 



73-5 



17700 



251-4 



116-2 



1775-8 



67-4 



187-3 



1779-5 



1797 



232-4 



1784-8 



340-5 



297-3 



1788-5 



92-8 



342-4 



1798-5 



36-3 



104-9 



1804-0 



203-3 



1720 



1810-5 



40-5 



2515 



1816-8 



2318 



328-5 



1823-2 



660 



46-8 



1829-5 



257-2 



123-9 



1833-8 



27-7 



176-4 



1837-2 



130-9 



218-0 



1844-0 



337-3 



301-2 



1848-6 



116-9 



3575 



1856-2 



3476 



90-4 



It will be seen that (omitting the results answering to the first 

 two epochs of the Table, which will be separately considered) at 

 the epochs of maxima Jupiter was in some position intermediate 

 between the point toward which the progressive motion of the 

 sun is directed (long. 253°) and the diametrically opposite point 

 (long. 73°, which is the longitude of the secondary magnetic 

 pole), reckoning from east to west from the first point to the 

 second. The average position is 183°, or in the vicinity of the 

 descending node of the currents of the secondary magnetic equator 

 (p. 206). Again, omitting the epochs 1755*7 and 1766*5, at 

 all the epochs of minima the positions of Jupiter fell in the other 

 half of the ecliptic, and his average position was in long 23°. 

 This is in the vicinity of the ascending node of the same equator, 

 which lies somewhat to the east of 343° (p. 206). If we con- 

 sider now the case of Saturn, we find that his average position 

 at the epochs of minima was 182°, or 183° if we take the first 

 two epochs into account. If we separate the positions that fall 

 in the two halves of the ecliptic, lying on opposite sides of the 

 line from 253° to 73°, we obtain the average positions 162° and 

 333°. If we include the first two epochs, the latter average 



