S.CIIiNCE-GOSS(r 



47 



atmosphere of Mount Hamilton, U.S.A., docs not 

 exhil>it the "canals" at all, and this has been 

 confirmed by one of the most skilful of planetary 

 observers. 



VV. Robertson. \.S., G.B.V.C., M.li.W.V. 



161I1 May, iSgi). 



I have been ver)' much interested in reading; Mr. 

 Robertson's communication. Me and I are really in 

 very close agreement. The instrument may be 

 accurately focu-.sed, but very soon the eye wearies 

 slightly, and its focus chanijes imperceptibly. If any 

 .xstigmatism be present, duplicity just becomes visible 

 in the direction of this weakness. With regard to the 

 failure of the Lick in.strument, it was perhaps to be 

 expected. Dawas, long ago, pointed out that 

 beyond certain limits, aperture did not help the 

 detection of planetary detail. The experience, al.so, 

 of the Mars section of the British Astronomical 

 .'\ssociation, is, that the best work has been accom- 

 plished by telescopes of between 9 and 10 inches' 

 aperture. The suggestion as to a possible action of 

 the Martian atmosphere, may, I think, be abandoned. 

 —Frank C. Dcintetl. 



VISITATION \).\\ AT 

 GRKEXW U II. 



O .\Tl'RDAY, June 3rd, was a splendid summer's 

 ^^ day, and a goodly company besides the 

 official visitors gathered at the Royal Observatory, 

 Greenwich, amongst others of importance being 

 the veteran Professor Simon Newcomb, Mr. S. P. 

 L;tngley of the Smithsonian Institution, and Prof. 

 Comu. All the instruments were open for in- 

 spection ; the Sheepshanks 6Jin. equatorial was 

 alone turned to the heavens. Owing to the state of 

 the atmosphere, the sun was the only object which 

 could be obser\ed. lie exhibited a solitary spot 

 surrounded b}' faculae, and two other groups of 

 faculae in its vicinit)". a little within the eastern 

 limb. 



Ihe building containing the Thompson equato- 

 rial, was completed last March by the addition of 

 the east and west wings. The erection is now- 

 cruciform in shape, having the central Observatory 

 tower, and four wings of three stories. These are 

 for the accommodation of the staff, the library, the 

 photographic and other records, the Observatory 

 publications, and a workshop. 



The new magnetic pavilion, about 350 yards east 

 from the Observatory, but within the park, was 

 completed at the end of September last, and the 

 standard thermometers and rain-gauges have also 

 been mounted within its enclosure. About the 

 same time the balcony was completed around the 

 building containing the aSin. telescope, and has 

 proved of great service. The electric light instal- 

 lation necessitates the use of accumulators, and a 

 new house for their storage was completed in 

 March last, but they h.ave not yet been installed. 



What was formerly the Astronomer Royal's 

 Official Room, has now been made an additional 

 chrononicter room, and will accon\modate 140 



chronometers. Between May nth, 1898, and 

 May loth, 1899, no less than 11,764 transits of 

 about 5,000 celestial objects have been obscrvcil 

 with the Transit circle. 



The New Alt-a/imuth has needed several altera- 

 tions, and was not considered completely satisfac- 

 tory until Kcbruary 23rd last. A chronograph is 

 being constructed by Sir Howard Crubb for use 

 with this instrument. The Thomp.son e(|uatorial 

 seems to be now quite satisfactorv ; the refiguring 

 of the outer surface of the 26in. object gla.ss having bee" 

 completed on June Sth, i8g8, and it was finally 

 approved, after a thorcmgh testing, in the following 

 .September. The 3oin. Cassegrain reflector at the 

 other end of the Declination axis, has had a new 

 mirror of slightly shorter focus ground for it, by 

 Dr. A. A. Common. This was received in Sep- 

 tember last, and has proved quite satisfactory. 

 This instrument was fouml to have a trick of run. 

 ning too fast, when west of the meridian ; a fault 

 due to too much weight on the refractor end of the 

 axis: a weight of 151b. running over a pulley, 

 since January loth, has remedieil this defect. It 

 has been employerl in photographing N'eptune 

 and its satellite, some double stars, and a few fields 

 of stars. The reflector has been used in obtaining 

 photographs of the new planet Eros, Neptune and 

 its nuxm, the comets of Brooks and Tuttle, the 

 Pleiades, the nebula in Andromeda, and the moon. 

 The 28in. refractor has been used for the micro- 

 metric measurement of 4ro double stars, the 

 majority having their components separated by 

 less than one second. With the I3in. Astrographic 

 equatorial phtitographic plates have been 

 taken cm 120 nights; but lor various reasons, 

 seventry-eight have had to be rejected. To com- 

 plete the sets only 24r successful photographs 

 remain to be t.aken. When the whole is com- 

 pleted, the damaged plates, mentioned last year, 

 will be replaced. 



Photographs of the sun have been secured on 

 195 days, before July 27th with the 4in. Dallmeyer, 

 and, since that date, with the gin. photo-heliograph 

 attached to the Thontpson equatorial. The photo- 

 graphs from India and Mauritius bring up the 

 total davs to 357 ; and some further plates are ex- 

 pected from the latter place, which may yet com- 

 plete the series. The photographs of the magnetic 

 disturbance on .September 9th last were remarkable. 



The mean declination of the magnetic needle for 

 1S9S was 16" 39.2' West; and the dip from January 

 to June 67' 1.4', and from October to December 



67°'n.3'- 



The mean temperature of 1898 was 51.3°, or 



1.8° above the average of the fifty years 



1841-90. The highest daily temperature, 92.1°, 



was on September Sth. Only once before has 



such a temperature been recorded in September, 



on the 7th of that month in 186S. During the 



ye.ir ending April 30th, 1899, 1,500 hours of bright 



sunshine were recorded out of a possible 4,454. 



The entire visitation was very interesting. 



Frank C. Dennett 



