1864. | Herscurr on the Solar Spots. 231 
searching former records, Dr. Wolf ascertained from the observations 
of Professor Boehm in 1833-4-5- 6, including the minimum of 1833-4, 
that the same phenomenon had then also occurred, the average lati- 
tudes of the spots in 1833 having been 9° 9’, while in 183 4, the year 
immediately subsequent to the minimum, it had risen by a similar 
sudden spr ing to 25° 0’, after which (as was also the case in Mr, Car- 
rington’s observations) it gradually declined to the normal state. 
Whether this be a general rule, remains to be seen. If so, it cannot 
but stand in immediate and most important connection with the 
periodicity itself, as well as with the physical process in which the 
spots originate. Meanwhile, however, an opportunity was thus afforded 
of determining the sun’s per iod of rotation by a great many equatorial 
spots, as well as by those in high latitudes. The results have been 
computed and synoptically tabulated with consummate skill and dili- 
gence by Mr. Carrington, in the extensive and laborious work already 
cited, and lead to the following general and highly-remarkable con- 
clusion—viz. that the period of rotation as deduced from spots in 
different latitudes increases with the latitude so far as 50° (beyond 
which no observations are attainable), or, in other words, that the 
equatorial regions of the photosphere revolve considerably faster than 
the polar. According to the law of dependence between the rotatory 
velocity and the corresponding latitude assigned by Mr. Carrington,* 
the difference amounts to no less than 5:89 days, the sidereal revolution 
at the equator being 30°86 days, and at the pole (supposing the same 
law carried on up to the pole) 24:97 days. At 50° hel. lat., the revo- 
lution would be completed in 28°36 days. 
Let us now consider what is implied in the law so disclosed. This 
will depend much on the supposition we may make respecting the 
rotation of the interior globe, of which we are left in complete 
ignorance. As extreme hypotheses we may suppose its rotation to be 
performed in the least of the above-named times, or in the greatest ; 
or, as a mezzo termine, in the intermediate period last mentioned. 
I. On the first hypothesis, the equator and the photosphere above 
it will be relatively at rest, and we shall have in analogy to the state 
of things prevalent here on earth, a region of equatorial calm, not 
much disturbed for some small number of degrees, &c., to the North 
or South. As the latitude increases, the photosphere, revolving in 
continually longer and longer time, will lag more and more behind the 
surface of the globe for the time beneath, the result being of course 
what we should call an “ East t wind,” or relative current from East 
to West, increasing in intensity with the increase of latitude, and 
attaining, according to Mr. Carrington’s formula, a maximum of in- 
tensity (estimated by the linear amount of momentary retardation) at 
* Mr. Carrington’s formula for the amount of diurnal rotatory movement in 
longitude for a spot in latitude 7 is 865’— 165’ (sin. 1)3, which is not very dif- 
ferent from 700/ + 165! (log. 2)?, which, howev er, he repudiates as representing 
the observations less closely. 
+ Great and habitual confusion arises from the use of the words East, West, 
Easterly, Westerly, as indicating direction. By an East wind, we would be under- 
stood to mean a wind blowing from the East; by an Easterly current or drift, 
whether of air or water, one which sets from West towards the Rast. . 
Ra 
