A drachm and a half to two drachms, according to the degree of intensity desired, added to the ounce of the above collodion, which should have remained a few days to settle before sensitizing, I find to act most satisfactorily; in fine weather it is instantaneous, being, after a good shake, fit for immediate use. If the sensitive collodion soon assumes a reddish colour, it is improved by the addition of one or two drops of a saturated solution of cyanide of potassium; but great care must be used, as this salt is very active. HUGH W. DIAMOND. * * * * * Replies to Minor Queries. _Portrait of Alva_ (Vol. ix., p. 76.).--There is a fine portrait of the Duke of Alva in the Royal Museum at Amsterdam, by D. Barendz (No. 14. in the _Catalogue_ of 1848); and MR. WARDEN will find a spirited etching of him, decorated with the Order of the Golden Fleece, in the _Historia Belgica_ of Meteranus (folio, 1597), at p. 63. The latter portrait is very Quixotic in aspect at the first glance, but the expression becomes more Satanic as the eye rests on it. LANCASTRIENSES. _Lord Mayor of London not a Privy Councillor_ (Vol. iv. _passim_; Vol. ix., p. 137.).--L. HARTLY a little misstates Mr. Serjeant Merewether's evidence. The learned serjeant only said that "he believed" the fact was so. But he was undoubtedly mistaken, probably from confounding {159} the Privy Council (at which the Lord Mayor _never_ appeared) with a meeting of other persons (nobility, gentry, and others), who assemble on the same occasion in a different room, and to which meeting (altogether distinct from the Privy Council) the Lord Mayor is always summoned, as are the sheriffs, aldermen, and a number of other notabilities, not privy councillors. This matter is conclusively explained in Vol. iv., p.284.; but if more particular evidence be required, it will be found in the _London Gazette_ of the 20th June, 1837, where the names of the privy councillors are given in one list to the number of eighty-three, and in another list the names of the persons attending the meeting to the number of above 150, amongst whom are the local mayor, sheriffs, under-sheriffs, aldermen, common sergeants, city solicitor, &c. As "N & Q." has reproduced the mistake, it is proper that it should also reproduce the explanation. C. _New Zealander and Westminster Bridge_ (Vol. ix., p. 74.).--Before I saw the thought in Walpole's letter to Sir H. Mann, quoted in "N. & Q.," I ventured to suppose that Mrs. Barbauld's noble poem, _Eighteen Hundred and Eleven_, might have suggested Mr. Macaulay's well-known passage. The following extracts extracts describe the wanderings of those who-- "With duteous zeal, their pilgrimage shall take, From the blue mountains on Ontario's lake, With fond adoring steps to press the sod, By statesmen, sages, poets, heroes, trod."