114 HISTORY OF THE [1850-60 185 
task in which it proved so efficient that it tended to mislead doe 
astronomers into the incautious assumption that, because many uni 
nebulae hitherto supposed irresolvable, were supposed to be seen sco 
in the field of this powerful instrument separated into their com- hac 
ponent stars, given sufficient magnification all nebulae would thus ere( 
prove to be distant clusters. Lord Rosse was awarded one of the de\ 
Royal Medals by the Royal Society in 1851, but he never received ma 
our Gold Medal, a somewhat curious omission which it is difficult pro 
to justify, though the explanation is presumably to be found in the is i 
fact that he was pre-eminent not primarily as an observer but can 
rather as an engineer, who developed to a high level of perfection 
the art of casting, grinding, figuring, and polishing large metal disc 
specula and in mounting them for practical observing. knc 
Another name which will always be associated with the early Fet 
use of large reflecting telescopes is that of William Lassell, who had tote 
been awarded the Gold Medal in 1849 and served in the office of it r 
President in 1870-72. Lassell was both a constructor and a skilful and 
observer, and not satisfied with our murky skies, he transported Rej 
his instrument, a reflector of 2-feet aperture and 20-feet focal recc 
length, to Malta in 1852, and observed with it there for some time, amc 
replacing it later with an instrument of double the aperture, which be c 
he used at Malta in 1862-65. The invention of the silver-on-glass be ; 
reflector threw the metal mirror out of commission, and a few years creg 
ago it might have quite confidently been maintained that no large ma£ 
metal speculum would ever again be undertaken. Lately, when sma 
we have seen the almost insuperable difficulties of casting very all ; 
large glass discs (witness the case of the Mount Wilson 100-inch, Noa 
where it took years before a suitable one could be obtained), it is is tl 
not quite so certain that we or our descendants may not see a was 
reversion to metal. The casting of a metal disc of any desired size insi< 
presents no insurmountable engineering problems. mea 
The last year of our decade saw the most momentous and far- 1 
reaching enlargement of the boundaries of astronomy : the applica- rapi 
tion by Bunsen and Kirchhoff of the principle of spectrum analysis The] 
(found by Stokes in 1853) to the determination of the constituents Noti 
of the solar atmosphere. Kirchhoff’s first paper on this subject was Feb] 
read before the Berlin Academy on 1859 December 15. His full natr 
memoir did not appear till eighteen months later, and the early and 
astronomical applications of the new research thus lie within the disa 
next decade. We may, however, just note that this announcement, ^ 
so important to us and marking off so clearly in our estimation the bodi 
opening of a new epoch, does not seem to have excited very much Botl 
attention among astronomers at the time. The Astronomer Royal The 
in his suggestions for the observation of the solar eclipse of July s 
i860, did not allude to the possibility of work of this nature ; nor phy*