1889.] on the Solar Surface during the Last Ten Years. 503 



disappeared, the apparition of fresh spots in tlieir midst, are facts of 

 constant recurrence. That facul^e are the first evidence of a coming 

 disturbance has never been observed at Stonyhurst, but a region 

 where fiicula3 abound has always been found to have previously been 

 occupied by a group of spots. Such an observation as that of the 

 birth of the great November spot of 1882, and other similar instances 

 are not wanting, in which a few dots, in a region of perfect calm, 

 suddenly develojDed into a vast centre of disturbance, is a strong 

 proof that the law which regards faculae as the constant forerunners 

 of spots, cannot be accepted as universal. Do not such instances as 

 these give some additional weight to the opinion that large spots 

 owe their origin rather to an external cause, as the prime mover, 

 than to the internal forces of heat and pressure and chemical affinity? 

 Might not the latter forces, however great, hold each other almost in 

 equilibrium until their energies are freed by the advent of an external, 

 though perhaps lesser, disturbing force ? The periodicity of sun- 

 sj^ots, their total absence for months, nay almost even for years, com- 

 bined with their enormous development and rapid changes about the 

 epoch of maximum area, seems to preclude the possibility of internal 

 forces, in a gaseous body, being the sole cause of such phenomena ; 

 although there appears to be no reason why these forces should not 

 exercise an overwhelming influence when called into play by an 

 external agent. 



The distribution of faculse, especially of small isolated patches, is 

 much more general than that of spots, many being visible even near 

 the sun's poles, and this has been forced upon my attention more and 

 more of late as we have aj)proached nearer the minimum of the cycle. 



Another point, which is often accepted as established, is the lagging 

 of faculae, and it is sometimes adduced as a proof that faculre are cast 

 up from a lower level, for thus, in possessing a less linear velocity 

 than the surrounding photosphere, they would naturally be left 

 behind. The observations of the present cycle can scarcely be said 

 to add to the stringency of this argument, as out of more than 4000 

 cases recorded in the Greenwich Tables, 74 per cent, lean neither 

 way, and of the remainder 5 • 7 per cent, show the faculae preceding, 

 against 20-3 per cent., which alone are in direct confirmation of the 

 assumed law. 



The general surfiice, with its ever varying aspect, can never be 

 adequately represented by the pencil, but in this case recourse must 

 be had to the instantaneous photograph. And yet it is true to say 

 that even in this branch of the subject much may be done by the 

 method of projection, and light may thus be thrown on many points 

 which could scarcely be settled by photography alone. I refer 

 particularly to any possible variation of tint in definite regions of the 

 solar disk, to rapid and continuous changes, and to such appearances 

 as the smugged areas in the photographs, which suggest at first bad 

 definition, but which are in reality evidence of a new form of distur- 

 bance not indicated by other phenomena. Watching the image of 



