408 



• KNOWLEDGE • 



[Mabob 10. 1882. 



while, bnl BOi'itiK Dip effort of tho mon incffrrluftl, ho bounded off 

 at full hjhhmI, mill l>y mcimii of liia iwrni-rfiil forrlcKd ho Hoiit <>no 

 dog fljiuK to tlir left iiiid thi> other to tho rijjht in wild confusion. 

 There ho htiHKl. with the dogs at a distance, iia much an to nay — 

 Daro to come n>,'nin, oitlier of you ! No further attempt at FightlnK 

 occurred. He in a %-cry |)owerful do(f, about 7 Htono weight, and 

 i* excellent in clearing the road of cattle and Bhcep before tho trap. 

 He rarely uses liia teeth, unless attacked, his forelegs being his 

 chief weapons. Thomas Fawcett. 



[317] — lict mo add to the instance given on page 209 that n dog 

 Uring at a boarding-house, at 61, Sussex-gardens (whore I used to 

 live), laughs in tho most human fashion, showing all his teeth. 

 This, with him, is a greater sign of ]>leasuro than wagging his 

 tail. 



P.S. — Is it not worth your while to correct the impression that 

 your correspondents have, that Darwin is to be accredited with being 

 the first biological evolutionist ? Cannot yon put Uorbert .Spencer's 

 position in this regard right ? J. li. U. 



[318] — I have a little black dog, which, if put out of tho room, 

 the door nhut, and a ball, or even a stone, hidden, will, when let in, 

 make a thorough search for it, first making a circuit of tho room, 

 smelling and looking the while, until he finds it, which ho accom- 

 plishes in a very short space of time, being as " prond as Punch " 

 when he has recovered it. The second time he comes in ho will 

 immediately go to the place where the stone was last hidden. Will 

 he not reason that as the stone was there last time it will be there 

 now also ? The other day I hid it in my pocket, which he found 

 in due time. Two days after I hid it again ; as soon as he was let 

 in he put his nose right into my pocket. One can imagine him finding 

 a ball by its smell, but how is it that he can find a stone sooner 

 than a human being could :•■ Gertrude A. Fryer. 



(i) 



ELECTEICAL IMAGES (228). 

 [319]— We have 



Pb {q'ai-q^, qn,'] = E^ <i„b-Eh i^, 

 and expanding in powers of b, and neglecting i' 



9.»=— rJ 9— 9»» ='''' + — T- + -; ; 



• •• 9'.»-9<.« 9»4= - ya^ "'■^5T:^>1 ^""^ 



and again 



L c (■(c--a-)J L c'J 



Hence 



Ic c(c'-a')J -L c'J 



c Li) c'(c'— a')J 



which is the required result. 



(iv.) 

 K. Statelet. 



DARWINISM. 



[320] — If tho opponents of Darwin's theory will consider 

 with care the following, from the pen of Prof. Fiske, of Harvard 

 College, they may, perhaps, be convinced. Ho says, in " Cosmic 

 Philosophy," that the Darwinian theory, when analysed, resolves 

 itself into eleven propositions, nine of which are demonstrated 

 tmths ; tho tenth a corollary to the nine predecessors; the eleventh 

 a perfectly legitimate postulate. 



1. More organisms perish than survive. 



2. No two individuals are exactly alike. 



3. Individual pcculi.iritios are transmissible. 



4. Those individuals whose peculiarities bring them into close 

 adaptation with the environment, survive and trausmit their off- 

 spring. 



5. The nur^'ival of the fittest thus tends to maintain an eqailibriam 

 betweon organisms and their environnient. 



0, Tho environment of every group of orguuisma is steadil/, 

 though slowly, changing. 



7. Every group of organisms mn«t, therefore, change in average 

 character, under penalty of extinction. 



8. Changes due to individual variation are complicated by the 

 law that changes set up in one part initiate changes in another. 



9. These arc further complicated by the law that structures are 

 nourished in proportion to thoir use. 



10. Tho corollary follows :— That tho changes thus sot up and 

 romplicatcd muat alter tho specific character of any group of 

 organisms, 



11. [Tho only postalate] Let it bo granted that, since the first 

 appearance of life, time enongh has elapsed to prodace all the 

 variation of species now seen. C. T. B. 



AURANGED SQLAKK.S. 



[321]— Your correspondent, E. V. R. (letter 231, page 273), 

 says : — " I believe these squares may bo arranged by placing the 

 diagonal numbers in what I may call their nn/»ral squares in the 

 first instance, and working up to them ; but I have only succeeded 

 with the square of 4." 



As I have succeeded with tho squares of 5 and C, I send my eola- 

 tions, which, I believe, will be found correct. 



A number in any place, added to the nambcrin the corresponding 

 place on the opposite side of the square, will make 26. 



The perpendicular, horizontal, and diagonal lines will make G5. 



A number in any place, added to the number in the corresponding 

 place on the opposite side of the square, will make 37. 



The perpendicular, horizontal, and diagonal lines will make 111. 



Emma C. Hootox. 



GHOSTS. 



[322] — Perhaps some of yonr readers may ^be able to supply 

 details as to the War Office ghost. All I now remember is the fact 

 which gave the case its n.ame and notoriety, viz., that as there waa 

 a discrepancy between the date of the apparition and that of the 

 official rctnrn of the death, further inquiry was made, at the 

 instance of tho relatives, by the War Office authorities, with the 

 result that the actual date of death coincided with the time of the 

 apparition, and that the former official return was incorrect. 



I do not see that instances of mistaken identity, and so on, hare 

 much bearing on a case like this. Of course, it is the strong and 

 not the weak cases with which science has to do. T. D. 



TELEPHONE. 



[323] — There is no great skill, or extensive apparatus required, 

 in tho construction of the ordinary Bell telephone ; and I can pro- 

 mise Mr. Mortimer (Query 222, p. 303) complete success, if ho will 

 carefully work out the following instructions. The telephone con- 

 sists of a small permanent magnet, a coil of fine silk-covered copper 

 wire, a diaphragm of very thin iron, and a case for containing and 

 fixing the whole. 



