NOTES AND QUERIES.

Otago Witness, Issue 1899, 13 April 1888, Page 20

NOTES AND QUERIES.

Quicksilvering of Copperplates (Miner, Otara).—The copperplate should first be annealed, i.e., heated to such a degree and in such a way that fine wood shavings placed upon the face surface will ignite. This is for the purpose of rendering the copper 'soft so that it more readily takes up the quicksilver. Next the surface requires to be moat carefully cleaned, which Is done by scouring it with wood ashes, briekdust, or very fine sand, and it is then rubbed perfectly bright with very fine emery cloth. Further operations in succession are:—(l) Washing with a strong solution of soda (to remove every particle of grease); (2) rinsing in e'ean water; (3) rubbing over with a Bolution of cyanide of potassium (strength, half ounce in one pint of water); (4) careful washing again with ■warm water for removing all the cyanide, which, if left, would dull the surface; (5) rubbing the plate with a mixture of very fine sand and some powdered sal ammonißC.apd with mercury in small doses sprinkled on the surface for to long as the copperplate absorbs it; (6) after the plate is well rubbed all over it is leit lying flat, with the mixture on, for about balf-an-hour, then it is rewashed with solution of cyanide of potassium, and more quicksilver is added until the plate does not absorb any more. If sodium ama'gam can be had the process is materially facilitated and shortened, for the rubbing of thiß amalgam into the plate can commence directly after the plate is brightened with the emery cloth. Inquirer.—The mutton shell fish belongs to the genus Haliotis. There are (nine or 30 varieties indigenous to New Zealapd waters, the largest and commonest being H. Iris. The outride of the shell is pale brownish white; the interior dark metallic blue and green, with yellow reflections and an iridescent play of colours. • Chips, West Coast.—The astronomical winter begins on June 21, although winter in New Zealand really commences a month or five weeks before that date. Mb John A. Miller, Armwtown, writes: — " Colonus," who in yonr last issue furnished a host of deeply interesting and valuable information in "Briefs," must have fallen into some mistake when he stated that water requires a fall of llin per mile to flow. The following is an extract from a recent French work on the subjects "An inclination of lin in 15 miles (jives motion to water; Sin inclination (fall) per mile in a straight, smooth channel gives a velocity of three miles per hour, while 3ft per mile in a straight, smooth channel produces a torrent. An excess of lOin per.mile puts a stop to ordinary navigation." Mr Geikie, in his "Text-book of Geology," endorses this latter statement, as the following extract will Emve: " The slope of a navigable river ought ard'y to exceed loiu per mile, or lin 633«." ltegarding the spefd of rivers the same authority says, '* The average rate of flow is much less than might be supposed even in what are termed swift rivers. A moderate current is about 1^ miles in the hour; even that of a torrent does not exceed 18in or 20in in thr hour." This estimate refers to streams a^ tbev are found in their natural state, and must not be confounded with that, given above for " a straight, smooth channel," as for instance a fluming box. At the present time, when the attention of practical mJners is directed to the saving of fine gold, these practically -ascertained facts should be of assistance to thoie miners who make experiments in this line, arid with the object of still further aiding them, I trust you will find room for the following extract from Mr Geikie's text-book : — " The transporting capacity of a stream depends (a) upon the volume and velocity of the current; (&) on the size, shape, and specific gravity of ths sediment, and (c) partly on the 1 chemical composition of the water. («) According -to the calculations of Hopkins the capacity of transport increases as the sixth power of the veloI city of the current; thus the motive power of the current is increased 64 timei by the doubling of the yejocity, JB9 times by trebling, |W!s «$8 by

quadrupling it. - If a stream which, in its ordinary . state, can just move pebbles weighing an .ounce has its velocity doubled by a flood' jtcan then '. sweep forward stones weighing, 4lb. Mr David' Stevenson gives the subjoined table of the power of transport of different veiooities of river cur-> . rents : — Inches per' Mile per , • ' . second. hour, 3 «- 0-170 Will just begin to work on fine clay. A X 0-340 Will litt fine sand. 8 — 0-4545 Will lift sand as coarse as linseed. 12 — C 6819 Will sweep along fine gravel. 34 "- 1-3638 Wiurollalongroundedpebblei ' lin in diameter. 36 •» 2-045 Will sweep along! slippery angular stones of the size of an egg. It is not the surface velocity, nor even the mean .; velocity, of a river which enn be taken as the measure of its power of transport, but the bottom velocity — that ie, the.tatn at which the. stream overcomes the friction of ltschnnnel. (6) 'Xheaverage specific.gravity of the stone in a river ranges between two and three timea that of pure water ; hence these stones when born along ot the river lose from a half to a third of .their weight in air. < Huge blocks which could not be moved by the tame amount of energy applied to them on dry ground, sre Bwept along when they have found their way into a'strong river current. The sbapa of the fragments greatly affects their portability, when they are too large and heavy to be carried in mechanical suspension. Bounded atones are, of course, most easily transported ; flat and apgular ones are moved with comparative difficulty, (c) Pure water will retain five mud in suspension for a long time: but the introduction of mineral matter in solution diminishes its capacity to do so, , probably by lessening the molecular cohesion of , the liquid. Thus the mingling of »alt with fresh water causes a rapid precipitation of the suspended mud. Probably each variety of river water has its • ■ own capacity for retaining mineral matter in suspension, so that the mete mingling of these varieties mar be one cause of the precipitation of sediment." The velocity of a sluice may be increased or lessened in two ways — namely, flnt by increasing or lessening the fall of a box or tail, race ; and second by inorensing or lessening the volume or quantity of water. But in all cases the • rate or rapidity of the flow lias been taken as the gauge in the above measurements. If, for instance, a tail race has a fall of 1 in 8. which may be considered a steep fall, and the volume of the water is doubled, the rate of the flow will be more than doubled. lam not aware that the exact rate of the increase of flow as affected by the increase of fall and of volume has been practically ascertained and tabulated. But perhaps some [ miner may be able to shed light on this subject. An interchange of experiences between miners on the flow of water in races, and its action upon different kinds of soil ; the amount of fall given to head and tail races, and other items connected with this subject would be of great general interest to many miners, and no doubt you, Mr Editor, would find room for such dissertations.— [Our columns are fit the disposal of miners for the pur- > pose suggested by Mr Miller.] P. C. Dunedin, writes :—'• A few weeks ago a correspondent nsked through Notes and Queries of your paper for the words of the poem 'Tom Logan,' by Glenledi, or the date on which it appeared in the Witness. I suppose he meant ' liob Logan,' beginning as follows :—: — Bob Logan was a plumber chiel, An' lang he sair't his maister weel ; ■ He sowther's pipes an' sootit drains . Wi' unco skeel an' muckle pains. If this be the same, so far as I can find out, it appeared on either the 19th or 26th April 1884 ; but if , this should prove incorrect I shall be most happy to supply him with an exact copy of the words." On reference to our files we find that the date was the 19th. We thank our correspondent for his courtesy, aud shall forward a copy of the Witness of that date to the inquii er. The Highlands and Islands.—" Auld Highlander," Kelso, writes : I nm sure Mr Blair deserves the thanks of. a'l Islanders and Highlanders for his interesting lecture on "lieminiscences of lilay and Highland Scenes," and Editor of the Witness also for publishing the same. Mr Blair gives a very good picture of the true characteristics of Highlanders in general, and I have no doubt it would be appreciated by all my countrymen and others scattered throughout Otago. I should like to see some other gentlemen delivering lectures of their reminiscences of other parts of the Highlands at the Gaelic Society. Novick, Fairfax.— (l) Select parcels tares ani linseed; tares, 10s 6d per bushel ; linseed, 14s per cwt. Quantities slightly lower. (2) Key to Barnard Smith'B School Arithmetic, 9s tid ; posted, 10s. Key to Chambers' Practical Arithmetic, 2s 6d; posted, 3s ; at A. Sligo's George street. Copies of the arithmetics to which these works aro keys are also ob» toinable at Mr Sligo's. Diseased Fowls.— Mr J. H. Labb, Waimatuhu, writes : In last week's Witness " Farmer, Oamaru." asks for a remedy for a complaint running through his fowl yard. I had some black and red game fowls troubled with the name dUease, and I cured my birds by giving three doses of castor oil in halfteaspoonful doses, and they all got well. Subscriber.— Yes. W. R. asks :— (1) If the wife owns the house can the hnsband vote as a householder at the election of a school committee. (2) Two persons live in ahouae, one, a single man , being the lessee, and the other, a married man with a family, engaged as a weekly servant to the former, which can vote at the election of a school committee.— (l) Yes. ( 2) Both are entitled to vote— the one as tenant of the house and the other as parent of children. Tubil Cain.— Write to Mr Didsbury, Government Printer, Wellington, who will supply you with a copy of the work it it is still in print. Rural Committeeman.— Your letter arrived too late for this issue, but it will appear next week. All correspondence must be in by Tuesday night ; see notification over " Country."