October 1, 1890.] 



KNOWLEDGE 



231 



Hcttcts. 



[The Editor does not hold himself responsible for the opinions oi 

 statements of correspondents."] 



RED, YELLOW, AND BLUE LIGHTNING. 

 To the Editor of Knowledge. 



Deab Sir, — Perhaps the following description of three 

 consecutive flashes of lightning seen by me during the 

 storm of last Sunday may interest you. At about 3.30, 

 while looking from a window due east, a flash occurred 

 stretching upward far towards the zenith as a jagged 

 i/t'lloir line. While looking with interest at the cumulus 

 cloud from which it seemed to spring, a second flash oc- 

 curred in the same region. It seemed in shape an oval 

 yellow patch with a brilliant blue line down the centre. 

 After an interval of a few seconds a third flash occurred, 

 which seemed to start from the same spot in the sky and 

 to stretch away horizontally to my right hand. It was 

 of a bright red colour. — Yours truly, 



28 August 1890. Freueuic Pincott. 



[Mr. Pincott's observation is interesting as tending to 

 show that yellow, blue, and red flashes may all take place 

 in the same region. It has been suggested tiiat yellow 

 and red flashes may be due to the ignition of dust in the 

 lower atmosphere, while the blue flashes are due to dis- 

 charges in the upper and purer air. It is possible that the 

 differences of colour may be due to differences in the in- 

 tensity of the discharge. There is a great difference in 

 the spectra of flashes, some appearing to give a nearly 

 continuous spectrum, while others give bright lines. — 

 A. C. R.] „.. 



EXTRACT FROM A LETTER FROM PROF. BARNARD. 

 To the -Editor of Knowledge. 



You speak of the larger picture illustrating your article 

 on the Milky Way as if it were an enlargement from my 

 photograph. It is the ordinal size. The others are 

 rt'diictionx. E. E. B.\rnard. 



To tlic Editor of Knowledge. 



Sir, — In the May number of Knowledge in " A Gully 

 in the Blue Mountains," C. Parkinson, F.G.S., appears 

 the following : " Snakes are wonderfully few and far 

 between . . . but under the improved medical treat- 

 ment gained by experience I doubt if a necessarily deadly 

 serpent (such as the cobra for instance) exists in Australia, 

 unless it be in tropical Queensland." With reference to 

 this statement, the writer must surely have heard of the 

 " death-adder " of Australia (drat/i, not diaf, as it is some- 

 times wrongly called). I think 1 can safely say that no 

 nuthcntir case has ever been known of recovery from the 

 bite of this species. I have known a dog die from the 

 bite in less than ten minutes. 



Another paragraph in the article is as follows: "An 

 old Australian informed me that all the best of the bird 

 life finds a habitat on the inland side of the great Water- 

 shed, that is the liegent, Bower, and Rifle 15irds." The 

 old Australian who gave this information nuist have very 

 little knowledge of his country. The home of the Regent, 

 Rifle, Dragoon, Coachman, &c., birds is in the dense scrubs 

 of the coast country ; whore I have seen the Regent 

 birds was in the linnya-liunya scrubs of the Burnett dis- 

 trict in Queensland, and 1 think, but cannot speak with 

 certainty, that they are not found farther south than per- 

 haps the 'I'weed IJiver District of N. S. Wales. I am 

 afraid that Mr. Parkinson must have obtained his infor- 

 mation from one of those persons, who are to be foinid in 



Australia as elsewhere, one who, knowing some portion of 

 Australia, considers that he is then entitled to speak " as 

 one having authority " of the whole of this great island. 



It is unfortunate that it is from these that visitors to 

 Australia often obtain their information, and it is only 

 after they have travelled in the country that they find that 

 many years residence in one colony does not necessarily 

 give a knowledge of the other colonies. The inhabitant 

 of N. S. Wales, if he has never left his own colony, will 

 know but little or nothing of Queensland, Western Aus- 

 tralia, or the Northern Territory, and the resident of the 

 western country is not the proper person from whom to 

 obtain information of the coastal country. 



It is in the scrubs of the coast country that the beau- 

 tiful fruit pigeons, rivalling the parrot in their plumage, 

 are to be found, not in the forest country of the interior. 

 The Bower bird has a more extended range. 



Sydney, N.S.W. Yours faithfully, 

 July 7, 1890. ..... G. E. Fatonc. 



THE HEPTAGON. 

 To the Editor of Knowxedge. 



Sni, — In an article on the regular heptagon, in the 

 February number of the Philoaojihical Magazim' for 1864, 

 Sir William Rowan Hamilton gives the solution of the 

 problem how to construct a hej^tagon, which was proposed 

 by Riiber in the early part of the jjresent century. Riiber 

 was an architect at Dresden, and his knowledge of mathe- 

 matics was probably entirely empirical. He seems to have 

 believed that his solution of this problem was mathema- 

 tically accurate ; and visiting Egypt at a period subsequent 

 to the discovery of his method, he came to believe that 

 the solution propounded by him was known to the ancient 

 Egyptians. He believed that the architects and builders 

 of the temple at Edfu, which is heptagonal, have left in- 

 dications of an esoteric nature, in the stone (to be inter- 

 preted by the initiate in after ages), showing how they 

 arrived at the construction of the heptagon ; and that 

 their method was identical with his own, which he had 

 discovered independently. Sir WiUiam Hamilton points 

 out that all the knowledge of ancient Egypt was in the 

 hands of the priests, and considers that Rober's hypothesis 

 is by no means untenable, and that the very method dis- 

 covered, or rather re-discovered, by Rober may have been 

 a secret in the keeping of the ligyptian priests, arrived at 

 by them possibly " after centuries of tentation." Sir 

 William, moreover, calls attention to the fact that although 

 the Euclidian construction of the regular heptagon is still 

 an unaccomplished problem, the mystery attachuig to it in 

 the age of ancient Egypt has long ceased to exist, and the 

 heptagon simply ranks with an infinity of H-gons, each 

 equally impossible to construct with mathematical accu- 

 racy. l)ut the I'jgyptians associated a special sanctity 

 with the mystical number seven, and the construction of 

 the heptagon was to them what the jihilosojiherx' stone and 

 the W'litcr of Life were to the empirics of a later age. 



Sir William Hamilton accompanies his article with a 

 diagram illustrating l-iober's mctliod. The diagram is 

 exceedingly complex, and to me it is not conceivable that 

 two persons should arrive, independently of each other, at 

 this same method. Nor do I think that any engraver, 

 proposing to himself the task of describing with accuracy 

 a regular heptagon, would choose Riiber's method. 



Sir ^\'illiam illustrates Rober's accuracy in the following 

 way: He sujiposes seven tunnels bored through the 

 earth in such a way that the seven tunnels represent the 

 seven chords of the seven arcs of the circle formed by a 

 section of the earth made at the equator and cut at right 

 angles to the polar diameter, such circle having inscribed 



