522 



- KNOWLEDGE • 



[Aphil 14, 1882. 



weight lii>nci>, vory miipli pn'siiarp. — K. n«ii.r.Y Wai.kkh, F.S.H. 

 Many tliriiikd. F. II. .1. II. You ciiii iiiii(fiiify n llnii to tin- iii/.o of 

 a bn<wor'« liorup, or of Junilio, by moaim of llip oxylijilro({i'n liiiitorii. 

 — 8(NK.X. Ccrtninly, the vdority nnd ili»tniir<« of any two |iliiiii-lii 

 nn coiincctpil by Kopler'n Inw. lliim, tako two pInnotH A nnd /(, 

 lot their poriiHlii bo j> niui /', tlipir diiitaiices rf nnd D, their vcloci- 

 tii'B r nnd f. Hy Kepler's law : — 



d' : ii'r.p' : i" 



■ £ — £. 



•'•p'" l"' d 



d D 



But obviously r : V'.: - '. -p 



" ' ' "p* • r*'- P' ' d '■ I" 

 ■.:d : d 



whence r : V:: y/V : ^d, or the velocities of 

 planotA arc inversely ns the square roots of the distances. — 

 J. LANKtiiiKAK. Yes, the darker part of the moon can often bo 

 ao«n. That part is lif^hted by the earth ; for when the moon is new 

 to us the earth is full to the moon. — C. K. Thohbitkn. Thanks. — 

 J, T. 1). How could the polo and centre coincide, however the 

 earth might be flattened ? If they coincided, the pancake earth 

 would bo of no thickness at all, which is absurd. Centrifugal 

 force at equator accounts for only a part of the difference. For 

 the nttractions at eqnntor nnd pole, independently of rotation, see 

 Todhunter's " Statics." The moon question rather more complex 

 than you seem to think. — J. B. MorFAT. We have not 

 "G. E. V.'s" oddrcss. — F. D. It seems to me there is no con- 

 fusion and no difficulty in the probabilities question. 



ELECTRICAL. 



Eccentric Chuck. — 1. Swan's lamps are 5s. each, the other forms 

 arc lOa. to 12s. Cd. 2. About twenty Bunsen cells, in good con- 

 dition, will light up a Swan lamp for tliroe or four hours at a time. 

 3. Speaking at the Royal Institution a few weeks since, Mr. Swan 

 said his lamps were reliable for 1,200 hours continnous burning; 

 but I believe they are now safe for at least 2,000 hours, or about 

 twelve months ordinary burning. — L. J. The Swan lamp (see pre- 

 ceding answer) may be obtained for 5s. of Swan's Electric Light 

 Company (Limited), 13, Mosley-street, Newcastle-on-'JVne ; 25s. 

 was the price, until recently, and further reductions, at 

 least, in the other systems may, perhaps, be expected. — Ash- 

 BRincE-RoBiNsox. A large-sized Pickford van might, perhaps, 

 hold a sufficient number of Danioll Battery cells to maintain fifteen 

 Swan or Edison lamps, but it is very doubtful. An induction coil 

 is of no use. You would require an engine and a dynamo-electric 

 machine.— A. W. B. To make a Grove's cell, get an earthenware 

 jar of, say, a quart capacity, into which put an amalgamated zinc 

 cylinder, and inside this a porous pot containing a sheet of platinum. 

 In charging, put concentrated nitric acid in the porous pot, and sul- 

 phuric acid, diluted with ten times its volume of water, in the outer 

 coll. Substituting a block of gas carbon (a waste product in gas- 

 making) for the platinum converts the Grove into a Bunsen. Gene- 

 rally the Grove is made in the flat form, the Bunsen almost invariably 

 being round. Is this lucid enough 'i You can buy either for about 

 6s. per cell, but can make them for about 3s. or 3s. G<l. 2. Your 

 best plan is to write to the various companie.s, offering your ser- 

 vices, and stating your qualifications. — E. C. H. A description of 

 the Brush machine is already written, and only waits its turn to 

 appear in Knowledge.— S. G. T. Keally, I am puzzled how to 

 answer your queries. However, I will try what I can do. In the 

 first place, the engine docs not produce electric sparks. Secondly, 

 friction is of no use to produce the electric light ; and, thirdly, 

 galvanic batteries are not verj- much better, although a light 

 can bo obtained from them; nor, fourthly, are the "mag- 

 netic coils affected by the action of the engine" beyond 

 being rapidly rotated before the poles of a magnet. Rend our 

 articles on " Electric Generators." " Tho Engineer," and " En- 

 gineering," for the past two or three years, contain the information 

 you re<|uire nlxjut gas-engines.— F. A. S. Wo shall describe the 

 gramme machine "when space permits," but it is more difficult for 

 amateurs to mnke than a modification of Siemens's machine, which 

 wo arc describing in our columns for tho "Amateur Electrician." 

 Uniuhort's " Electric Light" is, I think, the most recent work on 

 the subject ; but, although a good book, it is rather cnido in some 

 of its descriptions. 



MISCELLANEOUS. 

 G. M. GoHiiAM. Tho true theory of tho rainbow would be rather 

 too abatmso for our roadora ; albeit, if you had not lost tho one you 

 mention, wo should bo very willing to publish it. — M. T. H. Do 



you therefore reason that boenuso our grandmothers were idiot* in 

 mutters of dross, their granddanghtom nmA not mind licing raoroly 

 fixjlish ?— F. II. H. Your questions quite unsuitable. Our roadora 

 (and wu too) caro for none of these things. — FoNs Hasuusii. Do 

 not know. — Gbeookv. Very likely there is a good deal of elec- 

 tricity about the sun. Any details ? — P. H. Oabpkntee. We 

 have already arranged with a geologist for tho discussion of 

 such subjects. Our i^uenj column it defunct, and to it our 

 Ilrply column. — C. H. Bkee, M.D. Yes, but unfortunately for 

 your argument the egg is not an ellipsoid. — W. Mabel. We cannot 

 take up the subject. If the trade cares to try it, let them do so ; 

 they have our full and free permission. They have not asked for 

 it, but that is a detail. — J. Allen Beown. Quito so. Dr. Siemens's 

 theory will, however, never bo attacked seriously by science, for a 

 very sufficient reason — it has no life, therefore needs no killing. — 

 Anno Domini. " Oh, iMsh ! the worthy bishop said ;" for which 

 you will overhaul tho " Bab Ballads " — perhaps. — G. W. B. Y'es, 

 but perhaps Mr. S — ^, of London, will advertise as much for 

 himself. It is not our business to do so. — Besnabd Bati- 

 gan. See No. 21. — W. Robebts. Arabic names explained shortly. 

 Know nothing showing Cromwell believed in astrology. He was 

 superstitious in some things — strangely so for so strong a mind. — 

 J. A. Ubomley. Many thanks for the Dutch barometer. My 

 being the " fountain of knowledge " does not help me to get the 

 water in, but will try all three given methods. — Thomas Smith, 

 JuN. Nobody questions that character is shown by the shape of the 

 head ; so it is shown hy the chin, the nose, the cheek-bones. The 

 so-called science of phrenology, as advanced by Gall, Spurzheim, 

 and all their followers who really know what phrenology means, 

 asserts that underneath the so-called bumps are the cerebral organs 

 corresponding to the several qualities associated with those bumps. 

 It is this that science rejects. One can tell character as well from 

 nose, lips, chin, eyes, jaws, and so forth, as from cranial develop- 

 ment, and nine-tenths among so-called phrenologists (I suspect all) 

 really judge of character thus, and not from the bumps. Now I 

 venture to assert that there is as much reason for asserting that there 

 is an organ of Voluptuousness (Capital V., if you please. Monsieur le 

 Compositor) within the lips, and of Resolution within the chin, because 

 full lips indicate a voluptuous character and a prominent chin resolu- 

 tion, as for saying that there is an organ of Destruciivencssin the part 

 of the brain behind the ears, and an organ of Philoprogenitiveness 

 just above the nape of the neck. But the fact of the matter really is 

 that so-called phrenologists of our time know nothing whatever of 

 what Gall and Spurzheim really taught. — J. I never met with a man 

 of science yet who did not acrree with what, as you tell me. Professor 

 Boyd Dawkins said at Manchester. Sir W. Thomson's theoiy of the 

 meteoric origin of life is a joke, nothing more ; if he really main- 

 tained it, it wonld be a jest. — F. W. Halfpennt. Y'es, there can be no 

 doubt the Egyptian books contained nearly all that we find in the 

 books you mention, and a good deal more ; so did the Assyrian 

 stone records : and many go about saying, in favour of the account 

 you refer to, very much what Rogue Riderhood used to say for 

 himself {"Now say I 'm a liar.") But the subject is hardly 

 suited for our columns. We do not want to know what has been 

 taught, but what is. — W. J. Cant. We hope to publish the figures 

 drawn by compound pendulum, but, hitherto, the photographic 

 record is incomplete. The author of the paper you men- 

 tion has very kindly sent some red tracings, but the 

 red is aniline, and unsuitable for photographic effect. Your 

 stamped and directed envelope might be used if we could do 

 so without injustice to some 750 others. — -G. H. Mortimer. We can 

 no longer publish book titles. Y'our query unsuitable. — E. C. R. 

 Can you not look up Mr. Judd's book yourself K (Similiu- questions 

 — that is, questions relating to books — received from J. H., L. 

 Brown, W. Hartwig, M. Couybeare, J. H. Ludwig, and multitudes 

 of otheis. — Vacii'M. Query unsuitable. We must consider the 

 many, not tho few, or mere units. — M. B. Alder. Y'on think 

 lirant Allen very wicked, and also very silly, because he says, 

 " the daffodil has done so and so ; " others (myself, for 

 example) think his way of putting these things perfectly 

 delightful. What can I do, except to quote the old saying, 

 De ;;«,s(i6u.< non est disputandum ? But, tell me, where does 

 science stop and blasphemy begin ? Is it blasphemous to say 

 that child grows, or this tree thrives ? If you can allow 

 your mind to admit development on the small scale, can you not, 

 by any possibility, admit it on the larger scale too ? Can you not 

 see that to Him " who works in and through all things," there can 

 bo no distinction (as mth us) of large and small, long lasting and 

 transitory f For my own part, when I hear fanatics raving against 

 the general doctrine of evolution, I see in their ineptitude the 

 strongest evidence for evolution. Their inability to see that the 

 same Being who can arrange for the evolution of the fowl from 

 the egg or the man from the ombryon can also presumably 

 arrange for the development of the race also from a race of lower 



