1868. | Sir John Herschel and Modern Astronomy. 195 
Aberdeen ; in 1845, Sir John was President of the British Associ- 
ation; in 1848, he became again President of the Astronomical 
Society, having filled that honourable office in the years 1828 and 
29, 1840 and 41. In December, 1850, he was appointed Master 
of the Mint, which office he resigned in 1855. 
The influence of the Herschels on modern astronomy has been 
considerable. Added to great mechanical skill, remarkable powers 
of observation, and unwearying industry, we find in them high 
philosophic powers. As they pursued their inductive researches, 
they were ever producing, as efforts of pure deduction, thoughts 
which advanced the science to which they were devoted. ‘This 
has been most especially the case with Sir John Herschel. If 
any one doubts this, let him read his ‘ Preliminary Discourse on 
the Study of Natural Philosophy’ or his ‘ Essays, * containing his 
admirable addresses to the Astronomical Society. 
While devoting the powers of his mind so zealously to astro- 
nomy, it must not be forgotten that Sir John Herschel found 
time for the most careful examination of several other branches of 
science. The chemical action of the sun’s rays on both imorganic 
and organic matter forms the subjects of two memoirs printed in 
the ‘ Transactions’ of the Royal Society, which are full of the most 
suggestive experiments and thoughts. By those researches he 
greatly advanced the art of photography, and led onward by his 
investigations to the production of those exquisitely sensitive tablets, 
by means of which the luminous elevations which appear on the 
edge of the solar disc during a total eclipse have been faithfully 
copied and preserved, and the moon has been mapped by a most 
unerring pencil, the rays reflected from her own mountains and 
valleys. Nor must it be forgotten that in 1819 Mr. Herschel 
communicated three papers to the ‘ Edinburgh Philosophical Jour- 
nal’ on the Hyposulphites. He then explained the peculiar action 
of the hyposulphites on chloride of silver, which placed, after long 
years, in the hands of the photographer the only agent, hyposul- 
phite of soda, which can be employed efficiently to give permanence 
to his pictures. Without this agent the photographs of the solar 
clouds and the lunar mountains would be as transient as the rays 
by which they were at first delineated. 
Sir John Herschel has ever maintained the serene dignity of a 
true philosopher ; and his utterances of truths, which have inspired 
him with their divinity, have ever been received with delight by 
those who have listened to his subdued but impressive eloquence. 
How soul-elevating are the concluding passages of his address to 
the members of the British Association in 1845, with which we 
must close our notice of his labours :— 
* «Essays from the Edinburgh and Quarterly Reviews, with Addresses and 
other Pieces.’ Longmans & Co. 1857. 
