452 Scientific Proceedings, Royal Dublin Society. 
spots which have never revealed themselves to the regular Sun- 
observers, or appeared on the photographs of the Sun, which 
have now, during not a few years, been taken, on every clear day, 
at several observatories. After having alluded to the spot seen 
by Weber, which, but for its being found on the Greenwich and 
Madrid photographs would now have been considered a well 
authenticated apparition of an intra-mercurial planet, seen by an 
experienced observer, Professor Peters especially examines the 
observation by Lummis, on March 20, 1862, which is considered 
as very certain by Leverrier. By referring to his own diary, 
and to Professor Spérer’s observations, he shows how two 
ordinary spots have been noticed by Mr. Lummis, first one, and 
then, twenty minutes after, the other, which he thought was the 
same as the first one, which had moved in the meantime. He 
shows how the second position was vitiated by an error, which 
being removed the estimated distance of 12’, which was in con- 
tradiction to the sketch sent by Mr. Lummis to Mr. Hind, comes 
out all right. 
Almost simultaneously with the publication of Professor Peters’ 
article, another observation of a spot in transit by De Vico on 
July 12, 1837, preserved by De Cuppis (who saw a similar spot 
himself in 1839), has been announced in the Comptes rendus, 
vol. 88, No. 9. 
7. Planets and Satellites. 
Mercury.—The results of the observations on the transit of 
Mercury on May 6, 1878, have been printed by the Washington 
Observatory; but as far as we know, have not yet been distributed. 
Venus.—The fifteenth publication of the “Astronomische 
- Gesellschaft” is entitled “ Untersuchungen uber die Durchmesser 
der Planeten Venus und Mars nach Heliometermessungen, W&c., 
von E. Hartwig,” Leipzig, 1879, 4to. The heliometers which 
were used on the German Venus expeditions, and afterwards de- 
posited at the Strasburg Observatory for a detailed investigation 
of their constants, have, by the author, been used to take measures 
of the diameters of Venus and Mars during the years 1876-78. 
Venus was measured with two heliometers, and from all the ob- 
servations the diameter at distance unity (D+dD), and the 
constant error of the measures (7), were found by a number of 
