aul 
JANUARY 15, 1914] 
NATURE 
557 
Bay, so that ships anchored there might be able 
to observe the time-signals. The order to com- 
mence building was signed in 1822, but did not 
reach Fallows until 1825. After a change of 
‘Government in 1827, 10,000]. was cut off the 
estimates for building, so that when completed 
the observatory was a mere block of masonry on 
a desolate hill, without protection, an adequate 
water supply, or roads. The instruments were, 
however, installed, and some valuable observa- 
tions made. 
Fallows died in 1831, after eleven years’ work, 
full of anxiety and disappointment, and was suc- 
ceeded by Henderson, who remained at the Cape 
only one year, but crowded into that time an 
enormous number of observations of various 
kinds. His most permanently valuable work is 
his catalogue of positions of the principal southern | 
stars, obtained with similar accuracy to that of 
the northern stars at the same epoch, but his | 
_ his tenure of office a 7-in. heliometer, an astro- 
| graphic equatorial of 13 in., the Victoria tele- 
most striking discovery and that which his name 
invariably calls to mind, is his determination of 
the parallax of a Centauri. 
Henderson’s successor was Maclear. He re- 
mained director of the observatory from 1833-70. 
Maclear was a man of great energy and practical 
ability. He faced the difficulties which had dis- 
heartened Fallows, and from which Henderson 
had shrunk, and succeeded in making the barren 
hillsides into fertile grounds, in obtaining a pure 
water supply, in breaking the force of the south- 
east winds by planting trees, and establishing a 
communication with the main road to Cape Town. 
At the same time the scientific work of the 
observatory was carried on untiringly, both with 
the meridian instruments and equatorials. Owing 
to the smallness of the staff, the observations 
were not all reduced and published at the time, 
but Maclear’s successors, Stone and Gill, were 
able to publish these valuable observations. In 
addition, he found opportunities to extend help 
and infuse enthusiasm into the educational and 
scientific projects of the growing colony. 
Maclear was succeeded by Stone. He had 
been trained at Greenwich in the systematic school 
of Airy, and left as a lasting monument of his 
nine years at the Cape (1870-79) a catalogue of 
12,881 stars. 
Gill was appointed H.M. Astronomer on 
February 19, 1879, and retired on February 10, 
1907, after completing twenty-eight years of ser- 
vice. At the University of Aberdeen he had the 
good fortune to come under the influence of Clerk 
Maxwell, and gain inspiration from his teaching. 
His interest in astronomy began with the installa- 
tion of a time service for Aberdeen, which he 
carried out with the assistance of David Thomson, 
professor of natural philosophy. Shortly after- 
wards he purchased a 12-in. mirror, mounted it 
equatorially, and used it in measuring double 
stars, taking photographs of the moon and other 
observations. In 1872 he was offered charge of 
the observatory which Lord Lindsay was erecting 
at Dun Echt; he relinquished his business career, 
and accepted without hesitation the opportunity 
NO. 2307, VOL. 92] 
thus presented of devoting his whole time to 
science. 
Gill now entered on the congenial task of assist- 
ing in the design and erection of Lord Lindsay’s 
magnificent private observatory, and the testing, 
mounting, and adjustments of its numerous in- 
struments. Soon afterwards he accompanied 
Lord Lindsay to Mauritius to observe the transit 
of Venus, and in this connection made several 
important determinations of longitude. In 1877 
he made an expedition to Ascension, and from 
observations of Mars with a 4-in. heliometer, 
determined the solar parallax as 8°78", with a 
probable error of +o°012". 
Thus fitted by his training and experience, Gill 
found at the Cape Observatory ample scope for 
| his energy and for his mechanical and observa- 
tional skill. In 1879 the only instruments at the 
Cape were the non-reversible transit-circle, the 
7-in. equatorial, and the photoheliograph. During 
scope, presented by Mr. McClean, consisting of 
a 26-in. photographic telescope for spectroscopic 
work, with an 18-in. guiding telescope, and a 
new reversible meridian circle were all added to 
the equipment, and from all these instruments 
important results have already been obtained. 
With the non-reversible transit instrument observa- 
tions of fundamental stars, bright southern stars, 
and stars the positions of which were required as 
comparison stars for heliometer observations were 
carried on systematically, and particular mention 
may be made of a catalogue of 8650 reference 
stars for the astrographic work at the Cape. 
From the commencement of his tenure of office 
Gill urged the necessity of a reversible instrument 
for fundamental work. The project was not 
sanctioned, however, until 1897. The greatest 
care was lavished on the instrument, the building 
and the foundations. The full description, 
occupying one hundred pages of the book, and 
illustrated by many photographs and drawings, 
cannot be summarised in a short review, and only 
a bare mention can be made of the most striking 
and interesting features. Besides being revers- 
ible, the object-glass and eye end of the instru- 
ment are interchangeable, so that flexure may be 
eliminated, except for the sagging of the wire, in 
the mean of opposite positions. The microscopes 
are carried on iron piers, which are covered ex- 
ternally by non-conducting material, and are filled 
with water so that their temperature may be 
uniform in horizontal layers, and no tendency to 
twist be introduced. To detect any shift of the . 
telescope in azimuth, stable meridian marks are 
obtained by connecting optically the marks and 
collimator lenses N. and S. of the instrument, 
with points fixed on the solid rock at the bottom 
of deep iron cylinders. These have proved so 
successful that the movement of the pole in 
azimuth corresponding to the variation in latitude 
has been observed. The instrument is furnished 
with an impersonal micrometer for the elimination 
of magnitude equation from the observations of 
