July, 1905.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



183 



through want of proper assistance. Before his death, 

 in 1831, he had observed over 3,000 transits, and had 

 made several hundred circle observations, which were 

 subsequently reduced by Airy. Thomas Henderson, 

 who succeeded Fallows, remained at the Cape for 14 

 months, but in that short time he had made a large 

 number of first-rate observations, the most important 

 I)eing meridian places of o Centauri, from which he 

 found a parallax of about i''. 



Highly valuable observations were made by the next 

 astronomer, Sir Thomas Maclear (1834 to 1870), but 

 owing to inadequate assistance the reduction of a large 

 part of them had to be left to his successors. Mr. 

 E. |. Stone, F.R.S., who succeeded him, received, how- 

 ever, instructions to reduce them as quickly as possi- 

 ble, and from these observations three star catalogues 

 have been formed. 



In 1879, when Mr. (now Sir) David Gill took up his 

 duties, there were only three assistants on the staff and 

 three or four computers, the latter on the same footing 

 as at Greenwich; now the scientific staff numbers 12, 

 with 10 to 15 male and female computers. The instru- 

 mental equipment, too, has been greatly increased. In 

 1880 it consisted chiefly of the transit circle and a 7-inch 

 equatorial, but the additions since that date include 

 the Victoria telescope, the gift of the late Mr. F. 

 McClean, F.R.S., a new and specially designed transit 

 circle, an elaborate astronomical clock recently 

 installed, an astrographic telescope, employed chiefly 

 on the international " Carte du Ciel," a 7-inch helio- 

 meter, and numerous smaller instruments. 



Of the work already completed by Sir David Gill, 

 perhaps the most important is the determination of the 

 solar parallax from observations of the minor planets 

 Victoria, Sappho, and Iris. Over 20 observatories con- 

 tributed towards this work, and at the Cape, where 

 nearly all the reductions were made, more than 16,000 

 observations were made with the heliometer. The re- 

 sult is a solar parallax of nearly 8"'8o, corresponding 

 to a distance of the earth from the sun of 92,874,000 

 miles, a value generally adopted in national Epheme- 

 rides. We may refer also to the compilation of three 

 large star catalogues, the reduction of Maclear's 

 observations, the determination of stellar parallax with 

 the heliometer, the work done with the astrographic 

 equatorial for the " Carte du Ciel " and for the " Cape 

 Photographic Durchmusterung. " The latter is a cata- 

 logue containing the places, reliable to iH, and magni- 

 tudes of 454,875 stars from declination — 19° to the 

 south pole. Some 2,500 plates were taken for this, 

 and the arduous work of measuring them and making 

 the catalogue was undertaken by Prof. Kapteyn. 

 During the course of measurement a great number of 

 interesting variable stars were detected, also a star 

 with the greatest known proper motion. The measure- 

 ment of the plates, which is still going on, is entrusted 

 to ladies. So far about 800 plates have been measured, 

 containing nearly half a million stars. 



Another piece of work under Sir David Gill's super- 

 vision is the partly-completed geodetic survey of South 

 Africa. 



The Victoria telescope and accessories, with the 

 dome and attached laboratories, was the gift of Mr. 

 McClean, and is devoted to the study of astrophysics. 

 The dome is provided with a rising floor which is 

 worked by hydraulic machinery. The telescope itself 

 consists essentially of two parallel tubes tied together, 

 one for a 24-inch photographic lens, the other for an 

 18-inch visual: and there can be attached to it two 



large objective prisms or a large slit spectroscope for 

 determinations of velocity in the line of sight. Many 

 interesting spectra have already been photographed 

 and measured. 



The new transit circle has been specially designed to 

 be free from the effects of temperature change, and is 

 being used to make the most refined fundamental ob- 

 servations. It can be readily reversed in its trunnions, 

 can have the object-glass end and the eye end inter- 

 changed, and is fitted with Repsold's micrometer with 

 moving wire for observing transits. To bring this 

 installation into proper working order and to deter- 

 mine all such instrumental constants as division errors 

 of the circles, periodic errors of screws, and other 

 details, necessarily consumes time and demands much 

 patience, but in his last report. His Majesty's 

 astronomer stated that " the new transit circle will be 

 brought into regular catalogue observing work from 

 the beginning of 1905." The old transit circle is still 

 in use for the time service, an important part of the 

 observatory's work. The instant of Greenwich noon 

 is signalled every day to Simon's Town, Cape Town, 

 Port Elizabeth, and East London, and all the railway 

 clocks on the Wynberg line are automatically set every 

 hour, a system which is being extended to other 

 portions of the Government railways. 



To provide fixed meridian marks for azimuth refer- 

 ence, deep pits have been sunk, and on the bed rock 

 at the bottom of them the marks rest. A clock for 

 use in connection with the new transit circle has also 

 been installed, the pendulum of which swings in an 

 air-tight case, in which the air is automatically kept 

 at a imiform pressure and temperature. 



The Sovith AfricsLii 

 Museum, Ce^pe Town.. 



The only institution connected with zoology in South 

 Africa which is provided with a scientific staff and is 

 doing original work, apart from the mere acquisition 

 and arrangement of specimens, is the South African 

 Museum at Cape Town. This museum was founded by 

 the late Sir George Grey when Governor of the Colony 

 in 1855, and its first Curator was Edgar Leopold Layard 

 (a brother of Layard of Nineveh fame), who was well- 

 known as an enthusiastic naturalist. Layard was the 

 author of many books and papers on zoology, and like- 

 wise an excellent field-naturalist. His best known book 

 is his "Birds of .South Africa," of which the first 

 edition was published in 1867. The second edition, in 

 preparing which Layard was assisted by Dr. Bowdler 

 Sharpe, was completed in 1884, and has until quite 

 lately been the recognised book of reference on South 

 African ornithology. 



In 1872 Layard left the Cape to take up a consular 

 appointment in New Caledonia, and was suc- 

 ceeded by Mr. Roland Trimen, F.R.S., distin- 

 guished as an entomologist, and especially for his 

 knowledge of the Lepidoptera. Mr. Trimen held the 

 appointment for 23 years. His excellent work on the 

 butterflies of Cape Colony and surrounding districts 



