11 
SUN - SPOT PHENOMENA, OBSERVED AT 
STONYHURST COLLEGE OBSERVATORY 
By REV. A. L. CORTIE, January 13th, 1885. 
The Rev. S. J. Perry, F.R.S., F.R.A.S., had been announced 
to open the Session by a Lecture on “ The Government Expedi- 
tion to the South-West Coast of Madagascar to Observe the 
Transit of Venus.” Unfortunately, however, illness prevented 
the eminent astronomer from being present, and his place was 
taken by his assistant at Stonyhurst, the Rev. A. L. Cortie, the 
resumé of whose admirable address is here given. 
That there might be spots on the Sun was an idea that was 
never entertained before the days of Galileo. Jor in the eyes 
of an ancient astronomer the sun was typical of all that was 
most immaculate. Large spots were undoubtedly seen from 
time to time by the naked eye, but their appearance was attri- 
buted to small planets in transit across the solar disc. The 
discovery of sun-spots, however, was almost the first triumph of 
the newly-invented telescope, about the year A.D. 1610, the 
honour of the discovery being shared by Fabricius, Galileo, and 
Scheiner. Since their days, and more especially in recent times 
after the introduction of the spectroscope, the study of the solar 
surface has occupied the attention of distinguished men of all 
lauds, and we now see several observatories equipped with all 
modern appliances, devoted solely to this branch of astronomical 
_ physics. The Observatory at Stonyhurst has added its quota of 
results to recent researches upon the sun, and in order the more 
to fix our ideas, our future remarks will have special reference to 
the work carried out there. 
The method of observing the sun, as practised at Stonyhurst, 
is that of projecting the image formed by the 8-inch equatorial 
telescope on to a screen attached to the eye-end of the instru- 
ment. By this method the details of the solar surface can be 
studied or sketched at leisure; and moreover, by proper adjust- 
ment of the screen, the actual positions of the spots can be 
readily calculated. The phenomena observed upon the solar 
disc are of three kinds—spots, facule, and the network of dark 
and bright spaces which gives to the image its mottled 
appearance. 
The spots are of all shapes and sizes, some of them attaining 
enormous proportions. In a sun-spot three distinct parts may 
be distinguished—a less dark outer portion, which is bounded by 
