1830-40] ROYAL ASTRONOMICAL SOCIETY 75 
double stars, Dawes, began his labours on these objects about 
1830.* 
The brilliant discovery by W. Herschel of binary stars naturally 
led to attempts being made to calculate their orbits as soon as a 
sufficiently long arc had been described. The first to do so was 
Savary in the Connaissance des Temps for 1830, and he w r as soon 
followed by Encke in the Berliner Jahrbuch for 1832. Both their 
methods were perfect from an analytical point of view; but 
J. Herschel considered it a great objection to both, that they 
required four complete measures. At that time it was assumed 
that position angles could be measured without much danger of 
systematic errors, while this was not supposed to be the case with 
the distances. Herschel therefore rejected the use of distances 
(except for the determination of the major axis), and found the 
elements by a happy combination of graphic construction and 
numerical calculation.]* 
Herschel’s examination of the northern heavens was completed 
in 1833 May, and as soon as his preparations could be finished 
(even before all his previous observations were ready for publica 
tion) he embarked with his instruments for the Cape of Good Hope, 
in order to extend to the southern hemisphere the review which his 
father and he had made of the northern sky. Landing at Cape 
town in 1834 January, he lost no time in erecting his instruments 
in a suitable locality about six miles from the town, so that he 
could begin regular work on March 5. The last “ sweep ” 
with the 20-foot reflector was made on 1838 January 22, and thus 
was brought to a close an undertaking which is unique in the 
history of science, having been carried out in the course of thirteen 
years by one individual without any help whatsoever, and entirely 
at his own cost, including an expedition to a distant part of the 
earth lasting four years. No wonder that he was honoured in many 
w*ays on his return to England in the spring of 1838 ; his scientific 
friends and admirers gave him a hearty welcome at a festive 
banquet, before he settled down to the laborious task of preparing 
for publication the immense number of results of his expedition. 
Before Herschel left Slough in the spring of 1840 to spend the 
remainder of his life in Kent, he had to dismount his father’s 
famous 40-foot telescope, the woodwork of which had become 
dangerously decayed.]: This was done in 1839 December, a date 
which is of importance, as it serves to fix the time of a great advance 
* Memoirs, 5 , 135, 139 ; 8, 58, 61. 
f Ibid., 5 , 171 ; further applications of the method, 6, 149. Herschel 
returned to the subject many years afterwards in volume 18 . 
t The “ Requiem,” written by J. Herschel and sung inside the tube on 
New Year’s eve, 1839-40, is printed in Weld’s History of the Royal Society, 2 , 
195, and in the Astronomische Nachrichten, No. 405 (Bd. xvii.).