234 



KNOWLEDGE 



[Jam. 13, 1882. 



©UfltCSf, 



[162] — I.VSTBDMENT FOR Descwbixg El.tlPSE.— On paRe 160, No. 

 8, vol. 1, of Knowledge, Mr. Thomas Thoro gives a desifcn in Fig. 2 

 of an instniment for describing ellipses. I shall esteem it a favour 

 if he wll ilescribo the mechanism of it. — W. G. [It seemed to me 

 clear that tho stem of the instniment is intended to be held in a 

 fixed slantins; position, wliile the moveable branch is carried around, 

 sliding at the same time backwards and forwards on the fixed stem. 

 See Jlr. Thorp's rcplv. — Ed.] 



[163] — Sun- at his Ne.\rest. — At what season of the year are 

 the British Isles nearest the sun ? — Gko. D. Pattebson. — [About 

 Jan. 1, when the sun is nearest to the earth. — Ed.] 



[ICl] — XoN-AciiKOMATic Telescopes. — Would a 3-in. OG non- 

 achromatic telescope be of any uso for a beginner, or do the tints 

 vei-y much affect the clearness of the object ? Also is there any 

 simple way of overcoming the difficulty ? — G. W. L. — [Such a 

 telescope would bo of very little use; a very small acliromatic — one, 

 perhaps, an inch in diameter — would show much more, and a great 

 deal more conveniently. There is no way of correctijig t lie diffi- 

 culty. — Ed.] 



[165]- — HoRSERjVDisn. — What are the properties of horseradish, 

 and how does it act on the gastric juice when partake i: of? — T. 

 Hexerman. 



[166] — Shorihaxd Writing. — Can you, or any of the readers of 

 Knowledge, inform me which is the best system of shortlmcd ? 

 Has there been any system of late years which is thought an im- 

 provement on, or is more easily learnt, than Pitman's ? — -Skqpirer. 

 [There is no doubt whatever that Pitman's is the best, most easily 

 learnt, and scientific ; it is used by all tho most skilful steno- 

 graphers. — Ed.] 



[167] — Star Catalogues. — Will you kindly favour me with the 

 titles and dates of one or two star catalogues, both of ancient 

 (comparatively) and modern dates. Is there one to be depended 

 on of an earlier date than "Flamsteed's Catalogue of 1676?" I 

 cannot meet with one. — Alfred Champness. — [Flamsteed's is tho 

 earliest reliable catalogue. — Ed.] 



[168] — The Moon. — How is the absence of atmosphere and 

 water in the moon accoimted for ? Lockj'er, in his elementary 

 astronomy, saj-s that the dark portions of the moon are old ocean 

 beds, but does not attempt to account for the disappearance of 

 water. — G. P. — [The general belief is that, as the moon's mass has 

 cooled, the water originally forming lunar seas has been withdrawn 

 (soaked up as it were) into the moon's interior, the atmosphere 

 partly following, partly entering into chemical combination with tho 

 substances f^jrming the moon's surface. The moon probably shows 

 the condition the earth will have attained in two or three hundred 

 millions of years. — Ed.] 



[169] — Light and Lantern. — Required names of good book or 

 books for the study of "Light" with the use of the lantern. — 

 J. W. Stow. 



[170] — Scents. — What is a scent ? That it is a substance, I 

 suppose, will be generally admitted, for it is blown along by the 

 wind. It has occuiTcd to me that objects which omit scents do, for 

 tho most part, lose some of their weight or bulk — that is, the sub- 

 stance shrinks or becomes lighter, and if so it must tlirow off some- 

 thing in infinitesimallj' small particles or otherwise, which affect 

 the sense of smell in animals and human kind. Please explain 

 what is known about it. — Prester W. 



[171] — Choanites.. — Arc tho flints, commonly called choanites, 

 " silicified sponries from the chalk," or are they petrifactions of a 

 higher kind of animal, an anemone (if, for instance, indeed a sponge 

 can be called an animal at all, which seems to be doubtful with 

 Professor Ansted) ? Arc sponges, similar in form and arrangement 

 to the flints above named, found in a living state ? 1 have never 

 seen any; on tho contrary, living specimens aro similai- to tho 

 sponge of commerce, and to a fow only of the petrifactions ; ex- 

 hibiting per]>endicular tubes only, not lateral or horizontal, as in 

 ohoanites. Is tho spiral worm round the body or cup of tho 

 choanites, a parasite or a part of tho intestinal arrangement of tho 

 animal itself? I am aware that, if the worm is a parasite, such a 

 conclusion is fatal to tho idea of an anemone, for how could a para- 

 site obtain admission into the bodily substance of an animal so 

 organised ? And some choanites are found without the worm. 

 Nevertheless I incline to the belief that the choanite is the sea- 

 anemone silicified. — Prester W. 



[172] — Shortest Day. — Please tell me why the snn rises latest 

 (8h. 9m.) on Dec. 29, and seta earliest (3h. 49m.) on Dee. 12, 

 though the shortest day is Dec. 21 ; and also rises earliest (3h. 44m.) 



on .lunc 16, and sots latest (8h. 10m.) on June 26, though the 

 longest day is Juno 21. — J. K. U. P. — [llicse and similar anomalies 

 arise from our using the mean snn, not the real sun, to measure civil 

 time. At civil noon tho sun's centre is not due south, except on 

 certain days in each year, when the imaginary mean sun and the 

 real sun are together. — Ed.] 



[173] — Will you tell me, does the electric circuit Ijegin in a 

 battery at the zinc or at the copper plate in tho acidulated bath? 

 — [Not knowii : any more than whether action of sun on a planet 

 begins at the sun or at the jilanet. — El).] 



[174] — Sti-dents' Philosophical and Scientific Societies.-i-I 

 should be much obliged if you could tell me whether there are in 

 London any .Students' Philosophical and Scientific Societies, as I 

 should much like to belong to one. — Horace Davies. 



[175] — Helix. — In a recent lecture, Jlr. Spottiswoode said, 

 " The curve fulfilling these conditions will be a helix, whose pitch 

 is half a right-angle." What measurement is this ? In the most 

 ordinary form of hoUx, viz., a screw, tho pitch is merely a distance, 

 or, say, a straight line, tho space between two threads, measured 

 from apex to apex, parallel to the axis. What is this angle ? — 

 CoGiTo. — [Mr. Spottiswoode was, of course, (juite right. The pitch 

 of a helix is an angle, not a distance. It is the complement of the 

 angle at which the curve is inclined to the axis. — Eb.] 



[176] — Brick Clay. — Are the blue streaks in brick clay caused 

 by dissolved sea-weed ? — M. Webb. 



[177] — The NAUTiLrs. — Is it known for what use is the gut 

 running through the chambers of the nautilus ? — M. Webb. 



[178] — Satellites of Jcpiteb. — I have seen two of the satellites 

 of Jupiter with my naked eyes ; is that an unusual thing ? — M. Webb. 

 ■ — [Exceedingly. — Ed.] 



[179] — Falre Accumulator. — Wai you kindly tell me if the 

 quantify of electricity that a Faure Accumulator can contain 

 depends upon the size or upon the number of the lead plates? 

 Would one or two large plates contain as much as half-a-dozen 

 small ones r — R. P. H. 



[ISO] — The Pole. — Kindly state how Arctic explorers will be 

 able to tell exactly when they reach the North Pole. How will 

 they know that they are not some miles wide of the mark ? — 

 PiLULA. [Astronomical observations showing any given star at 

 same height all round the heavens would give their place near 

 enough. — Ed.] 



[181] — Bees. — I want to keep bees, and want a list of the best 

 honey-producing flowers to cultivate in my garden. Will you be 

 good enough to tell me where to get this knowledge ? — Pilula. 



[182] — Evolution. — Will Dr. Andrew Wilson or Mr. Grant Allen 

 kindly let me know what is the probable origin of Evergreens ? I 

 have tried hard to think it out for myself, but am unable to see 

 what advantage it is to the plant, unless it be that it gives it an 

 opportunity of spreading while the other plants are at rest, or 

 that the exposure to the cold makes it more hai-dy, and, there- 

 fore, better adapted to carry on the struggle for existence. — 

 Plesiosaurus. 



[183] — Effects op Efflcttla on Health. — In our dye works 

 here we use a great quantity of bullock's blood, which comes to ns 

 in a highly putrid state ; in fact, the smell of it at a distance of 

 several yards from the tanks is overpowering to strangers, and 

 causes one to cough. Is it healthy to work amongst it ? This is a 

 question which has often occurred to me, and, natm-ally, I look to 

 the health of those who work during a whole day with this 

 cflluviura continually ; but, instead of finding them weakly, and 

 exhibiting symptoms of pulmonary disease, I am astonished to see 

 them grow fat and ruddy, and in many cases persons of known 

 weakly constitutions have improved much in health by being put to 

 work in tho dye-house. — J. Maccinslane. 



[184] — Almanacs and Celestial Maps. — Could yon kindly 

 inform me through your" Correspondence Column" — 1. Where can 

 I get " Dietrichsen's and Hannay's Astronomical Almanac " [no 

 longer published. — Ed.] and "The Nautical Almanac" for 1882, 

 and the price of each (where are they published) ? [Murray, price 

 2s. 6d.— Ed.]; 2. The publishers of " Middleton's Celestial Atlas " 

 and of " Gall's Atlas," and the price of each ? — W. Habdy. 



He that wyll wryte well in any tongue, muste folowe thys councel 

 of Aristotle, to speake as the common people do, to thinke as mse 

 men do ; and so shoulde euery man onderstande hym, and the iudg- 

 raont of wyse men alowo hym. Many English writers haue not 

 done so, but vsingo straunge wordes as latin, french, and Italian, 

 do make all thinges darke and harde. — Roger Asciiam, 1545. 



