3S0 



♦ KNOV/LEDGE ♦ 



[May 1, 1885. 



LETTERS RECEIVED AND SHORT ANSWERS. 

 Miss E. Dalton offers to supply Mr. Gansby with a male sala- 

 mander. She has, she writes, had a pair for seven or eight years, 

 has been very snccessful in rearing the young ones, and is anxious 

 to find a happy home for them. — Thomas Ayer.s. Suum cuique. If 

 any pubhshed discovery of yours has been utihsed in recent scientific 

 expositions, of course you ought to have the credit of it. — Peote-\. 

 Your question, put without qualification, has very little meaning. 

 The comet of 1729, at its nearest to the earth, was more than 

 308,000,000 miles fi'om us, and was visible for six months ! A 

 comet in 1847 was followed until it was three and a quarter times 

 the distance of^the earth from the sun. When first perceived (with 

 difficulty) by Donati, the comet of 1858 was 240,000,000 miles 

 from us. No comet has been, so far, seen at the distance of 

 Jupiter, Biela's comet was seen for the last time in 1852. The 

 nebulous fragment picked up by Mr. Pogson at Madras in 1872 

 was two months behind the computed time of this comet, so 

 that astronomers are unanimous in the belief that this was 

 not a part of comet Biel.a. — E. L. G. I can only regret, 

 sincerely, that you attach such conditions to furnishing " D. L. X." 

 with the formula for the profile of his gnomons — because I can 

 have none of them. " R. A. P." had as much — or as little — to do 

 with the replies as the Mahdi himself. Like other paradoxers, you 

 seem to be possessed witli the extraordinary idea that you have a 

 direct equitable claim to occupy the pages of a scientific journal 

 with expositions of your thesis, and thence to defy the universe to 

 disprove it. If you think that a watery comet (whatever that 

 may be) caused a deluge on the earth 5,000 years ago, why not 

 ventilate so very philcsophical a hypothesis before the Geological 

 Society at Burlington House ? You would there confront scores 

 of men infinitely more familiar with traces of diluvial action on 

 the earth's surface than yon can possibly be, and the value of your 

 " evidence " would be shown by the result of the discussion which 

 would probably ensue. If a majority of men who have devoted 

 their lives to the study of the earth's crust coincided with you, you 

 should have space and to spare here to proclaim your triumph. If, 

 on the other hand, they regarded the " Watery Comet" as a mere 

 frantic attempt to bolster up an untenable legend, then the question 

 would be settled at once and for all by the only persons entitled to 

 decide ex cathedrd on it. — Alfred Capper. Received with thanks. — 

 H. A. B. When Mars is favourably situated in opposition, his polar 

 snow cap may be perfectly well seen with a three-inch achromatic. 

 Jupiter's belts are at all times visible in such an instrument. 

 A fortiori, a splendid view of these phenomena is obtainable in an 

 eight-inch reflector. The Milky Way consists of millions of stars — 

 not necessarily, however, large stars rendered seemingly minute 

 by their great distance. See " The Universe of Stars." A purist 

 would say " each side of the way," and not " either." — A. J. W. 

 1 have asked " F.R.A.S." to reply to your query, and ho says, " As 

 far as my experience extends, Jupiter's fourth satellite always 

 appears dark in transiting the face of the planet, but it enters on 

 to and leaves the planet's limb as a more or less bright spot. Y'our 

 correspondent's account of the dimness of the satellite when 

 projected on the dark sky after quitting Jupiter's face 

 ia very interesting." — J. Webb. What " F.R.A.S." means 

 is that the planet has got into an unfavourable posi- 

 tion for the observer, not that it is absolutely invisihle. How 

 high is it above the horizon now when it is dark — say at 8h. 30m. ? 

 — CiiAS. A. LoxTON suggests that Mr. Butler should furnish the 

 etymology of the scientific names given in his papers on " Our 

 Household Insects." — Dr. Lewins. Much that you say is beyond 

 contnadiction. To select a single illustration, I feel quite as 

 strongly as you do how utterly baseless a figment is that of a 

 " vital principle," and have said before here that it would be as 

 wise (or as foolish) to call in a "watch principle " to explain the 

 action of a chronometer. Upon such a question as this discussion 

 would clearly be permissible. But an impartial re-perusal of your 

 own letter must show you that you trench npon questions upon 

 which argument could not be admitted here without wholly alter- 

 ing the character of this journal. — W. R. Kennan. Y'ou will find 

 that the typographical errata to which you invito my attention 

 were subsequently corrected. When the papers are reprinted, 

 this correction will, of course, be made in the text. On April 

 18, at llh., Jupiter's satellites appeared in an ordinary inverting 

 astronomical telescope to the left of the planet in this order : IV., II., 

 III. (below), I, (above). — Rev. Charles Voysey. My sole end is, 

 as far as in me lies, to be rigidly just and impartial. Many thanks ; 

 it is scientifically accurate as it is eloquent. — M. H. E. — Thanks. 

 The question was not whether "a farinaceous diet .... is (or is 

 not) best suited to the tropics," but whether it is (or is not) the 

 fact that vegetarian races have invariably succumbed to flesh- 

 eating ones. Of course, if the rionecr chooses to assert that the 

 vegetable-eating Hindu is the incarnation of bravery and soldier- 

 like qualities, and the "modified meat-eater," the Sikh, is an arrant 



cur, lion est meum eontra aucforitalcm Senatis dicere. For aught ] 

 know the editor may possess facilities for deciding the question on 

 the spot, and by means of a " set-to," between a Sikh and a 

 Hindu in his own compound, to gauge their respective powers 

 and pronounce deBnitely on them. But I fancy that 1 could 

 find an Englishman to thrash the couple of them if necessity arose. 

 ■ — F. W. RuuLER. Received with thanks. — Uncle John. Precisely 

 as though travelling in an absolute vacuum. — J. B. Rundell, in 

 sending me his new Stenographic Alphabet, adds that his system 

 will be explained to the Shorthand Society, 55, Chancery-lane, at 

 8 p.m., on May G. We shall hear what professional shorthand- 

 writers think of it then. — W. Mathews. I can hardly find space for 

 a reply to an irrelevant criticism in another journal. — B. Jackson 

 wishes to be informed how " Crystal Soda" is made for washing pur- 

 poses. — Robert Millar. I am ignorant of the book you name, but 

 Williams & Norgate, of 14, Henrietta-street, London, published one in 

 1877 with the same title. — S. Gr — N. I don't know myself ! Inquire in 

 either of the localities in which the use of the word was presupposed. 

 — Holmdale. I cannot tell the "exact" variation of the compass at 

 Cheltenham ; but, if you assume it to be 19° west of north, it will 

 be more than sufficiently accurate for your purpose. You can 

 hardly obtain a meridian line by means of Polaris without more 

 elaborate appliances than you possess. If you are not satisfied 

 with one obtained by compass, you had better wait until the 20th or 

 21st of June, when the declination of the sun remains sensibly the 

 same for twenty-four hours. Fix a knitting-needle truly square to 

 a perfectly flat board, and round the point at which the needle 

 enters the board describe a number of concentric circles. Level 

 your board accurately, and your needle will be perfectly upright. 

 About 8 a.m. notice where the shadow of the top of the needle 

 touches one of your circles, and make similar observations for the 

 next hour or two at intervals, carefully marking the points of con- 

 tact of the shadow with the circles. At equal intervals after noon 

 repeat these observations. Join the pairs of points thus obtained, 

 bisect the lines joining them, and through these points of bisection 

 draw a line to the base of the knitting-needle. This last line will 

 coincide with the meridian. Negretti & Zambra, Casella, or other 

 meteorological instrument-makers are the people to consult about 

 an anemometer. — MusAFiR. Observations of occnltations of stars 

 by the moon, if accurate, do possess scientific value, both as 

 affording means of determining longitude and of correcting the 

 lunar tables ; but their reduction is most operose, and involves a 

 really tremendous amount of calculation. If you can obtain a copy 

 either of Chauvenet's or Loomia's "Practical Astronomy," you will 

 soon see what you have to face ; a remark which equally applies to 

 ascertaining longitude from a solar eclipse. The reduction of lunars 

 is far more simple. If you have observed any occnltations of stars, 

 at accurately determined local times, at the moon's dark limb, yon 

 should transmit them to England for comparison with the corre- 

 sponding ones at Greenwich. Moon-culminators are beautiful in 

 principle, but fail in practice. A large number must be taken both 

 preceding and following the moon, and with both of her limbs 

 illuminated in turn, to get a result worth anything at all. Expe- 

 rientia docet. Your suggestion, re mean time sun-dials, that the 

 gnomon might be constructed, so that one edge would serve for one 

 half of the year and the other for the remaining half, seems worthy 

 of attention ; but I am personally ignorant what form such edges 

 should theoretically assume. — David Glasgow, Jun. Thanks 

 for your offer; but you deal with subjects on which two 

 — in fact, three— of the permanent staff of this journal are 

 competent to treat. On receipt of a stamped and directed 

 envelope, your communication shall be returned. Your letter, 

 dated the IGth ult., did not reach me until long after that, — 

 Miss Gertrude Nash. Scarcely suitable for a paper devoted 

 wholly to science. It will be returned on receipt of the regulation 

 stamped and directed envelope. Reviewing already in skilled 

 hands.— Commentator. I heartily agree with yon. "Poor old 

 England !" is certainly a solecism in the mouth of any Canadian, 

 gentle or simple. With our resources, material, intellectual, and 

 moral, we may gauge such an utterance at its true value. Perhaps, 

 though, the man who employed it was thinking of the Government, 

 and not of the mighty British Empire. He may have been reading 

 the French, German, Austrian, or Russian newspapers, and sup- 

 posed that their comments referred to the mass of Englishmen 

 generally, instead of to a wholly insignificant fraction among them. 

 — F. W. 11. We are, as you say, absolutely in accord ; but you will 

 see that I have perforce closed the discussion here. You have 

 contributed too much of value and importance for me ever to 

 complain of your " persistence." — Aug. J. Harvey suggests the 

 appointment of public interpreters at all ports, terminal railway 

 stations, &c. 



There is every possibility of the Clifton Extension Railway to 

 Avonmouth being opened for passenger traffic during the summer. 



