428 
NOTE A. (§ 21.) 
THE VELOCITY OF LIGHT: ITS “ASTRONOMICAL DATA n 
AND “ EXPERIMENTAL PROOF.” 
The following correspondence may be read with interest, especially con- 
sidering that another edition of Mr. Chambers’s Handbook has recently 
issued from the Clarendon Press, Oxford : — 
“ Royal Institution of Great Britain, 
“ November 21 st, 1863. 
“ Sir, — My attention has this day been directed to your Victoria Toto 
Ccelo, in which (p. 48) you do me the honour of a reference to my Handbook 
of Astronomy : — 
“ ‘ How often have we been assured of the “certainty” and experimental 
confirmation of the old 192,000 miles per second as the velocity of light. 
(Vide Airy’s Lectures , Worms’s Earth audits Mechanism, Chambers’s Hand- 
book of Astronomy, &c., in locf 
“Two courses of comment suggest themselves on reading this passage 
— a personal and a general one. As regards the former, I think that in 
citing my remark as an exemplification of your own, you have unwar- 
rantably laboured to make me the object of a gratuitous sneer, which I hereby 
complain of. 
“If you will read again the passage in p. 166 of my book, you will find 
that I have done nothing but casually and incidentally advert to a statement 
which (though I believed it) it was no part of my province as an astronomer 
to discuss critically. Any person reading what you have said, without being 
acquainted with the original, could scarcely fail to infer that I was a dogmatic 
pleader for the indisputable accuracy of the aforesaid figures ; whereas, so far 
as my opinion was concerned, I said next to nothing on the subject. I shall 
trust to your candour in a future edition either to modify the passage or to 
append a copy of this note. 
“ The general question is one which I can scarcely believe ought to be 
argued. Surely a physicist may make a mistake as well as any other man, 
and is entitled to a rehearing when he becomes possessed of more reliable 
results. For my own part, I entertain a high opinion of the value of Fou- 
cault’s discovery, and you will find it adopted in my second edition, now in 
a forward state for issue early next year, the first being all but exhausted. 
“ I am, Sir, your obedient servant, 
“J. Reddie, Esq. “ G. F. CHAMBERS. 
“P.S. — If you will point out any real errors in my book, you will be 
conferring a favour equally on the public as on myself.” 
[Answer to the above Letter .] 
“ Bridge House, Hammersmith, W. 
“ November Z6th, 1863. 
“ Sir, — I have delayed answering your letter of the 21st inst , in order to 
ask some friends whether they could discover anything either ‘unwarrantable’ 
