SCIENTIFIC SUMMARY. 
421 
1836-1870, Dr. Fuhg obtains, “ Astron. Nach.,” 2,040, u 32' 2 //, 99 as tbe dia- 
meter of the sun deduced from 6,827 measurements. 
The Transit of Venus seen from Pekin . — Mr. Watson, at one of the Sep- 
tember meetings of the French Academy, read a long and interesting paper 
on the observations of the Transit of Venus made at Pekin station, of which 
he was the chief. The question of the atmosphere of Venus, and the diffi- 
culty of determining the exact time of real contact were examined at full 
length. M. Leverrier expressed his decided opinion that the determination 
of the parallax of the sun by this method was useless unless some unex- 
pected service should be rendered by photography for solving the difficulty 
raised by Mr. Watson. Mr. Watson tried to discover to what height the 
atmosphere of Venus was liable to cause optical disturbances by its illumina- 
tion by the sun, and he found it to be fifty-five miles, about l-70th the dia- 
meter of the planet. — See 11 Nature,” September 16. 
Death of Professor cF Arrest. — “ Silliman’s American Journal” says that 
Professor Heinrich d’ Arrest, of the University of Copenhagen, died on the 
14th of June, in his fifty-third year. The most important of the labours of 
this distinguished astronomer were the construction of two catalogues, the 
one of nebulae observed by him at Leipzig, the other of nearly 2,000 nebulae 
observed by him at Copenhagen. For these observations the Royal Astro- 
nomical Society of London awarded to him this year their gold medal. 
America's Loss of an Astronomer. — It appears that Joseph Winlock was 
born February 6, 1826, in ! Shelby County, Kentucky. Graduating in 1845 
at Shelby College, he afterwards held the professorship of Mathematics and 
Astronomy in that institution until 1852. The remainder of his life was 
passed chiefly at Cambridge, Mass. ; but he spent some months at the U.S. 
Naval Observatory in Washington, and for more than a year was at the 
head of the mathematical department of the U.S. Naval Academy at Anna- 
polis. He was twice made superintendent of the American Ephemeris, 
finally quitting this office in 1866 to take the post of Phillips Professor of 
Astronomy at Harvard University, and in that capacity to serve as Director 
of the Observatory. He held this office at the time of his death, June 11, 
1875. His last illness was short, and did not appear dangerous until a few 
hours before its termination. 
The next Return ofEncke's Comet.— “ Nature ” of September 16 says that 
“ the appearances of this comet at nearly ten-year intervals in 1819, 1829, 1838, 
1848, 1858, and 1868 took place under circumstances which were more or 
less favourable for observation in this hemisphere ; these conditions, how- 
ever, will not attend the ensuing return to perihelion, which, with the mean 
motion found by Dr. von Asten for 1875, neglecting the small effect of per- 
turbation, would occur about the 27th of July, 1878,* and if the path in the 
heavens be calculated on this assumption, it will appear that observations 
will hardly be practicable except in the southern hemisphere in August. 
The nearest approach to this tract is that which the comet followed in 1845, 
when a few observations only were obtained with difficulty at Rome, Wash- 
ington, and Philadelphia. With regard to the effect at perturbation upon 
the length of this comet’s period since the year 1819, when its periodicity 
was first detected, it may be remarked that the longest revolution was that 
from 1842-45, which extended to 1,215-6 days, and the shortest, that from 
1868-71, 1,200*2 days ; difference of extremes, 15| days. 
