ASTRONOMY: G. E. HALE 
383 
solar equator. One of the spots may be replaced by several smaller 
ones, or even be absent altogether, its place in the latter case being 
indicated by calcium and hydrogen fiocculi. Small companion spots, 
of either polarity, may attend either member of the pair. The char- 
acteristic feature of the group is the presence of magnetic fields, of 
opposite polarity, in the regions including its eastern and western 
extremities. 
Deferring until another occasion a discussion of the probable origin 
of bipolar groups, it will suffice for present purposes to emphasize the 
necessity of recognizing the existence and importance of such pairs. 
The following quotation from a valuable paper by Father Cortie, based 
upon a study of some 3500 drawings of spots made at Stonyhurst Col- 
lege Observatory, is of special significance in this connection: 
The chief type, however, of which the above mentioned are in most, pos- 
sibly in all, cases but phases, is the double spot formation, with a train of 
smaller spots between the two principal spots of the group, the whole group 
generally drifting into more or less parallehsm with the solar equator. In 
this form the principal spot, which eventually becomes a normal spot of regu- 
lar outhne, is generally the leading spot, but in many cases it is the following 
spot, while sometimes the preponderance in area alternates between the two, 
as the group traverses the disk. In yet rarer instances both the chief spots 
develop as regular spots. (Astrophys. J., 13. 261, 1901.) 
As the preceding (western) spot of a bipolar group usually lasts longer 
than the following spot, and is likely to be the larger of the two, we 
may take it as the dominant member of the group, and classify the po- 
larities of northern and southern spots accordingly. Single spots, fol- 
lowed by a train of fiocculi, are classified in Table 1 as preceding spots. 
Under the headings V and R are given the number of spots for which 
the ''marked strip" of the compound quarter-wave plate transmitted 
the violet or red component respectively. The spots of the old and new 
cycles (observed before and after the recent sun-spot minimum) are 
tabulated separately. 
TABLE 1 
TABLE 2 
OLD CYCLE 
NEW 
CYCLE 
in 
HEMISPl 
Pr. 
Spots 
Foil. 
Spots 
Pr. 
Spots 
Foil. 
Spots 
V R 
V R 
V R 
V R 
N 
5 0 
0 1 
0 13 
10 0 
s 
2 16 
8 0 
9 1 
1 7 
OLD CYCLE 
NEW CYCLE 
N 
S 
N 
s 
Mean 0 and No. 
of spots 
10° (7) 
9° (22) 
22° (11) 
26" (6) 
Weighted Mean 
9.0° (29) 
23.2° 
(17) 
