29 
star is visible with telescopes of moderate power. Comparing 
the light-curves for 1864 and 1865 with the curve laid down 
from the observations made in 1863 after the discovery of the 
variable, I conclude that a maximum occurred about the 
14th of October, 1863, the magnitude being*8'5. The next 
maximum occurred on the 12th of September, 1864 — mag- 
nitude, 8'3 ; and the third on the 9th of August, 1865 — 
magnitude, 8*9. The interval between the first and second 
maxima is 334 days, and that between the second and third, 
331 days. The mean period is therefore about 332 days. 
In the Astronomische Nachrichten, No. 1523, Dr. Schonfeld 
states that this star was observed on the 8th of September, 
1855, in zone 7^4 of the Bonn “ Durchmusterung,” and 
estimated to be of the ninth magnitude, but was invisible 
to Professor Argelander with the telescope of the Bonn 
meridian circle on the 9 th, and with the heliometer on the 
20th of November following, and was therefore not inserted 
in the “ Bonner Sternverzeichniss,” its existence evidently 
being considered doubtful. Guided by the course of the 
star’s light-curve, I conclude from the Bonn observations that 
a maximum occurred about the 12th of August, 1855. The 
interval between this date and that of the last maximum, 
August 9th, 1865, is 3,650 days, during which time the star 
passed through eleven complete periods of change. We find 
' therefore that the value of the mean period is 33 T8 days, a 
result agreeing very closely with that derived from my own 
observations alone. 
An inspection of the diagrams which accompany this com- 
munication will show that S Delphini increases in bright- 
ness much more rapidly than it diminishes, and that the 
course of its light-curve is more irregular after than before a 
maximum. During the last apparition it rose from the 
thirteenth magnitude to a maximum in 48 days, but was 89 
days in descending again to the same magnitude. When at 
minimum it is below the 13^ magnitude, and it remains 
