96 



♦ KNOWLEDGE 



[Jan. 30, 1885. 



to be numbered, one lias merely to look at any of our public clocke 

 at even a moderate distance. Take, for instance, the great clock 

 at Westminster from tlie south side of the bridge. From this 

 point the observer will be unable to distinguish one numeral from 

 another, yet the time can be ascertained just as approximately and 

 as readily as if each numeral were distinctly seen. 



The numerals might be altered to Chinese, Greek, Egyptian, or 

 Assyrian, and the public, unaware of the change, would be able to 

 tell the time just as well as before; distinctly showing that when 

 distance renders the numerals indistinct, the vahie of each is well 

 known from its relative position, and, therefore, the boundaries of 

 the hours do not require to be numbered. It may surprise many 

 to know that with tlie two '"hands'" projjerly proportioned and 

 adjusted, the time can be ascertained readily, and with suthcient 

 accuracy for all ordinary purposes, from a perfectly blank dial, 

 without a mark of any description ! 



In the " dial," or rather disc, now submitted to your notice, tlie 

 numerals and minute subdivisions are superseded by twelve plain 



radial marks coloured red (or pink, or " lead," or other suitable 

 colour). These, with the intermediate spaces, which indicate the 

 minutes, and the " hands," wliich measure as well as point the 

 time, are each equal in width to one-sixtieth of the circumference of 

 the divisional circle. The "hour hand" (the one making one 

 revolution in twelve hours) moves a distance equal to its width in 

 twelve minutes. The "minute hand" moves the same distance in 

 one minute, and, when subdivided near the outer circle, the time 

 can be measured, as the hand advances, to various fractions of a 

 minute. " Afternoon time " can easily be obtained by adding 

 twelve to the hour, thus, j past 3 p.m. = 12 + .3.15 = 15.15. 



This "clock-dial" would have the adv.antage of being easily 

 understood, and that by all nations. Jloreover, the time can be 

 ascertained more accurately, more readilj', and at a much greater 

 distance than from an ordinary " clock-dial " of equal diameter 

 with Roman numerals, as used in the ancient methods of measuring 

 time by the sun. C. H. and C. W. Thompson. 



LETTERS RECEIVED AND SHORT ANSWERS. 



G. Johnson. Yet another request (this time from the London 

 and North- Western Railway Library and Literary Association !) 

 for the gratuitons supply of Knowledge and of Health, with 

 which last-named paper I have nothing, proximately or remotely, to 

 do. Why the proprietors of a journal should give it away I rather 

 fail to see. If I went to Euston Station and requested a free pass 

 over the line, I suspect that I should be politely but firmly shown 

 to the door of the general manager's oflice. For the Htli time I have 

 neither power nor authority to make an eleemosynary distribution 

 of a paper which 1 merely edit. — J. T. N. kindly answers part of 

 Mr. .7. Farrar's query by saying that " Karoo" (Hottentot Karuoa, 

 bard), is a name Mpplied to the open clny tints of Southern .Vfricp, 



which often rise, terrace-like, to considerable elevations. — J. E. 

 DiMBLEBY. Prior engagements prevented my attendance at your 

 lecture on " Universal Time." I am, however, but little concerned 

 indeed with a system of chronology which so violates familiar 

 facts as to make the world less than 0,000 years old ! — 

 James Gran. Forwarded to the conductor, though I fe.-^r 

 that the time at his disposal is very much too limited to 

 admit of it. — H. W. T. It has just struck me that Dr. Maekay's 

 " Manual of Modern Geography," published by Blackwood & Sons, 

 would answer your purpose. — Lyons. Your parrot is suffering 

 from irritation of the skin caused by its diet. Meat, hempseed, and 

 oleaginous food will either or all of them cause it.— F. La.nkestek. 

 I had not a reporter at my disposal on the day specified. — X. In 

 14 oz. of water that has been boiled aud cooled dissolve loi grain.-; 

 of Shred Castile soap. Put this into a bottle and the bottle into 

 hot water in a saucejian, and shake it up until the soap dissolves. 

 Now set the bottle aside for a few hours for the impurities to sub- 

 side, and finally pcur off the clear liquid and shake it thoroughly up 

 with 05 oz. of pure glycerine. — Edwin WooKin. I must., of course, 

 see it before pledging myself. — Selwvn Toorne. Mary thanks 

 indeed. 1 heartily reciprocate your good wishes. — L. S. Get 

 the volume of Lardner's " Handbooks of Natural Philosophy," on 

 " Hydrostatics and Pneumatics," the new edition published b\ 

 Crosby, Lockwood, & Co. — W. W. I do not know the address of 

 Mr. Kinnear, the inventor of the self-lighting gas-burner. Perhaps 

 he will advertise it. — Chas. H. Swinstead, wishes to know, in con- 

 nection with the chapters on " Modern Domestic Economy," 

 whether a description of the method of getting rid of liquid refuse, 

 such as bath water, that from kitchen sink, &c., will appear r 

 inasmuch as the earth-closet fails to provide for this. — J. H. Garfit. 

 The reply must come through these columns. To append your 

 address would be to convert your question into an advertisement. — 

 G. W. If we assume B C to equal A B in your figure, it is evident 

 that a gun sighted to strike B (when fired from A) would not strike 

 C when tired from B, with the sight intact. Take, for simplicity, 

 what is called point-blank range. Now, be the trajectory ever bo 

 flat, the ball will begin to fall the instant it leaves the muzzle. 

 Hence the gun must be elevated more or less above the horizon, 

 even when tired at a horizontal object. If, though, we were tiring 

 vertically, the axis of the bore produced must pass through the 

 object aimed at. The range varies with the angle, the maximum 

 range, in vacuo, being obtained with an angle of -45° of elevation. 

 For, calling R the range, V the initial velocity, a the angle of pro- 



R = V-sin2a 

 jection, and g the force of gravity, ; whence, obviously, 



R is greatest when 2a = 90° or a = 45°. The way in which this affects 

 the (light of shot over a given linear interval is pretty obvious. It 

 is, though, utterly impossible to teach even the rudiments of gunnery 

 in an answer like this. — W. A. Sheppard. Do you seriously suppose 

 that 1 am going to insult the readers of Kx<.tWLEDGE by the insertior^ 

 of your hopeless twaddle about "The Immobility of the Earth?" — 

 Commentator. Assuredly I have not the slightest wish to quarre) 

 with you, but you sent me a goodly part of a quire of paper con- 

 taining observations dv omnihiis rcbu>< et q>i ihu^dam alii^, and I said, 

 periphrastically perhaps, but pretty plainly, what my opinion of 

 their worth was. I am not concerned to deny that you are " a man 

 of genius," nor even that "a kind of inspiration" may have 

 dictated j'our comments ; all I feared was that our readers would 

 fail to recognise this. Perhaps some evolutionist will reply to your 

 question as to whether sexual distinction was originally acquired 

 by natural selection ? and to your second one, as to why th^ 

 carnivora were created, if vegetables were the natural food of 

 animals ; and whether man himself may not have acquired his taste 

 for flesh-food and his concomitant supremacy by natural selection 

 too? Many thanks for the most picturesque photographs. — John 

 Kirk. I regret that these columns cannot be made the channel for 

 appeals for charities (however deserving they may be) save as 

 advertisements. — R. T. Shea. There is an excellent work on book- 

 binding by J. W. Zaehnsdorf, published by Bell & Sons, London, 

 and a smaller and cheaper one by Crane is just advertised by L. 

 Upcott Gill. 



The Bennet-JI.hkay Caules.— The success of the new Commer- 

 cial Cable Company, from a business point of view, has been very 

 satisfactory, the number of messages being, it is said, 1,000 on the 

 fourth day after the opening of the system for public traffic. Dr. 

 Jluirhead has applied an improved system of duplex to the cables, 

 which, we undcr.stand, transmits practically double the number of 

 messages, which the simplex or ordinary system sends. Press 

 messages are charged for at the rate of ild. per word ; and commer- 

 cial messages are subject to a slidlng-scale of prices, which has its- 

 upper limit at Is. 8d. per word, and its other rates depending on 

 the number < f mcs ages annually sent by the party. — Eiifiiiiecrhn/. 



