Diic. 2, 1881.] 



• KNOWLEDGE • 



101 



©ufiir^. 



[2U"' — Gaepex Tripod Staxd foe Telescope. — Could any of 



1 .in- rcadcx-s tell me how to make a cheajj gai-deii tripod stand for 



3-iii. glass, and where to get the several parts ? The cheapest 1 



.an buy is £1. Is., and that seems so dear for so simple a thing. — 



IcXOHAMlS. 



[30]— Solar Heat. — With respect to the sun beiiiir hot, will you 

 kindly explain to nic why some countries are warmer than others ? 

 If it is because they arc nearer the sun than the cold ones [but it 

 is not — Ed.], why, then, should not the top of a mountain be 

 warmer than the bottom ? On a man going into a tropical country, 

 he naturally gets brown-burnt by the sun (?). Does the sun act 

 directly on the man, or docs it first enter the earth, and the man, 

 as it were gets the reflection ? — Warmcs. 



[31] — Intknsity Coils. — Can you inform me how to estimate the 

 maximum battery-power which may be used with any given in- 

 tensity coil, without incurring the risk of destroying the insulation ? 

 Can yon afford me any practical hints as to the best way of restoring 

 one so damaged withont having recourse to a coil-maker? I 

 presume it will be necessary to replace the secondary coil with a 

 new one — but how ? — A. 



[32] — ExGRAViXG ox Copper. — Want to know the usual method 

 of engraving on copper, what the plate is covered with, and the 

 materials used ? Is it sulphate of copper and salt, or what ? 

 Engraver cannot get any clieap handbook bearing on the subject. — 



KXURAVER. 



[33] — AsTROXOMiCAL SLIDES. — Can any of your readers give me 

 a few hints how to prepare the above for a lecture on popular 

 astronomy ; also, how to make a good opaque black for same ? — 

 C. J. S. 



[34] — Three-handed Chess. — Can any of your readers inform 

 me of a way of playing chess with three players only ? The fom-- 

 lianded g.ame is well known to me. — Geo. H. Verney. 



[35] — With reference to the calculations concerning the four 

 asteroids and the magnitude of the third satellite of Jupiter, 

 have there been found any great differences since 1846 ? — S. S. S. S. 



[36]— Laplace's Theory. — Do you consider Laplace's conclu- 

 sions with reference to the physical forces and evolution sound, 

 as tar as we now know ? — S. S. S. S. 



[37] — Vestiges of Creation. — Who is the author of " Vestiges 

 of the Natural Historv of Creation," and do you consider it reliable ? 

 — S. S. S. S. 



[38] — Density of Xeptuxe. — What is the density of the planet 

 Xeptnne, and how many of his satellites have been discovered ? — 

 S. S. S. S. 



[39] — The Moox's Rot.wiox. — The moon turns once on its axis 

 in exactly the same time that it takes to revolve once round the 

 earth. Is there any law or theory ag to the cause of this, or is it a 

 mere coincidence ? — C. 0. K. 



[40] — Fixe Drilling. — Professor Edward C. Pickering, of Harvard 

 College, says that in undertaking to measure the intensify of the 

 light of the satellites of Mars, he 1-ad occasion to need an extremely 

 small hole. Among the artisans who essayed to furnish what was 

 required was one who had succeeded in making a hole edgewise 

 through an old-fa.shioned three-cent piece, and another who had 

 pierced a needle tlirough from end to end. A hole about the 

 twenty-five-hundredth part of an inch in diameter was finally 

 secured. — {Puhlic Opinion, Nov. 19, 1881, p. 658.) Have you any 

 knowledge of the above? Assuming that there is no mistake, an 

 account of the mechanism employed, and of the boring instrument, 

 would be of interest. — A. T. C. 



[41] — The Plaxet Vllcax. — Is anything more knoivn of the 

 planet Vulcan ; and is it believed to be certainly in existence ? — 

 S. S. 



[42] — Magxetoscope. — Is there any instrument made for the 

 purjiose of measuring the amount of magnetism, and also electricity 

 in the human body ? I think I have heard of a " magnctoscope," 

 but know no particulars. — S. S. 



[43] — B.Sc. AXD D.Sc. Examinations, Loxdon Uxi^-ersity. — I 

 am desirous of obtaining such a knowledge of science as would 

 enable me to answer such questions as are set in the B.Sc, and 

 even the D.Sc. examination papers of the University of London. 

 What books would you recommend for this purpose ? I shall be 

 extremely obliged for an answer to this. — Ax Exthcsia.st. 



[44] — iLLfMiXATiox OF THE SoLAE SYSTEM. — Ma}' I, as a reader 

 of KxowLEDGE, requcst you to give me and my fellow readers some 

 sound instruction on the subject of the new theorj' started by Mr. 



Collyns Simon, on the " Solar illiimination of our system " ? I have 

 seen attention called to it by several foreign periodicals, but none 

 by the English. Are wc to accept it as possible, or reject it as 

 impossible ?— V. A. T. 



[45] — Cavse of Gravity. — What is the cause of gravity ? There 

 is an interesting article, if I recollect rightly, in the old '" Encyclo. 

 Lend.," giving the views of Sir Richard Philips on this matter. 

 Philips believed that all the phenomena attributed to attraction 

 might be accounted for by the laws of motion. — Meter. 



[46] — Plaxetary Rings. — Are these not evidences of matter 

 more or less plastic beyond tlie solid planetary nucleiTS, the pheno- 

 mena presented by the denser and cloud portions of the atmospheres 

 of planets, ranging themselves centrifugally, in belts ? This globe, 

 in my view, would appear belted in other planets. This explanation 

 might be illustrated experimentally. — Meter. 



[47] — Optical Illi-sions. — Are these not all due to the simple 

 law of contrast ? — Meter. 



[48] — Teisectiox of ax Axgle. — I shall be glad if any of your 

 readers can inform me how to trisect any angle. A small diagram 

 will greatlj- assist. — Euclid. 



[49] — LiFTixG Max's Weight. — Could you kindly inform me how 

 it is that four men appear to lift a fifth so easily when they all 

 inspue their breaths together ? Is it simply a trick, or is there 

 some scientific explanation of it ? I should esteem it as a favour to 

 have an answer in your next issue. — D. U. B. 



[50]— Wasted Exergy ? — A certain amount of energy is supplied 

 to an electric lamp in the form of current electricity. A small part 

 reappears as heat, the rest as light. What form does the energy 

 radiated as light ^■ibrations take as the light is constantly absorbed 

 by surrounding objects ? — A. H. H. 



[51] — Botany Lectures. — Can the Editor or a reader of Know- 

 ledge tell me of any first-class lectures on Botany, embracing such 

 subjects as are not included in the ordinary lectures given at the 

 various science schools, but are required for the S. and A. Honours 

 Exam. ? Do not any of the masters of the subject teach, either bj- 

 lecture or correspondence ? — Nemo. 



[52] — Microscope. — Can anyone oblige by recommending what 

 they consider from experience to be the best microscope for botani- 

 cal and biological work ; cost, mth all necessary appliances, not 

 to exceed £10. ? — Nemo. 



[53] — Suggestion. — Botanical Papers. — If the Editor of 

 Knowledge should see fit to introduce into his useful and interesting 

 paper a series of articles on botanical subjects, I think many 

 readers would welcome them with pleasure, as the subject is one 

 that is now so widely studied, and the new discoveries and theories 

 of the learned do not appear in the text-books till long after date. 

 A column devoted to this subject would surely be as appropriote to 

 Knowledge as a chess or whist column. — Nemo. 



[54] — Chemical Questions. — 1. In testing a solution of ferro- 

 cyanide of potassium with chloride of ammonia, ammonia in excess, 

 and hydrosulphm'ic acid, no precipitate was obtained. Could you 

 e.vijlain whj' no precipitate was thrown down, since iron is one of 

 the third group of metals ? 2. Strong solutions of bisulphate of 

 potassium and prt:i.'?.sic iodide were separately treated with tartaric 

 acid. No effect, fven when stirred on a glass sm-face. Why was 

 there not a white precipitate following the com-se of the stirring- 

 rod ? — Castor and Pollux. 



[55] — Future of Greek Verbs. — Is there any rule for the 

 lengthening or otherwise of the vowel when forming the future of 

 a pure verb in Greek. For instance : — 



"fiXfw makes "tiXijirw 

 KaXfto ,, Ka\t(T(jt} 



riftato „ 7i,i,)(7w 



(\)Ow „ cpanu, 



Why should the e be lengthened to >( in "tiXew and not in naXiui ': — 

 Castor and Pollux. 



[56] — Can yon kindly recommend a book covering the chemistry 

 for the South Kensington Honours Syllabus ? — Castor and Pollux. 



[57] — The Great Bear. — In what latitude wotifd this constella- 

 tion become invisible for three months of the year, by dipping 

 below the northern horizon ? Is the upper pointer (Dubhe) the 

 most western star of the constellation, and the tail star (Benct- 

 nasch) the most eastern ? What is the difference of celestial 

 longitude between the most eastern and most western stars of the 

 constellation— i.e., how many hours and minutes of longitude does 

 the Great Bear spread itself over ? The Surya Siddhauta, a text- 

 book of Hindu astronomy, which seems to teach a medification 

 of the Ptolomean system, attributes to this constellation a cycle 

 of 2,700 years. The translator (Rev. Ebonezer Burgess) is at a 

 loss to faiow what this refers to. Can you solve the difficulty ? 



