Apkii.. 191; 



KNOWLEDGE. 



137 



equal to that of the Earth. It is absurd to suppose that they 

 could also support such a period and also a period half 

 as long again. To do this all the planetary markings would 

 have to be in two places at once — in his eye and his 

 telescope perhaps they appeared to be — but on the planet 

 never. If the markings charted by the older observers 

 were real they should be easily visible in the vastly better 

 telescopes of the present day. In ordinary air— the better 

 the telescope the more immaculate the planet appears. It 

 is only under very favourable climatic conditions that the 

 observer can be assured of their reality. They are harder 

 to see than the canals of Mars. It is therefore foolish to 

 quote the early observers, whose evidence in the light of 

 modern research is thus proved to be valueless, for they never 

 saw canals on Mars. Nevertheless to them is owing the credit 

 of opening the question. The radial markings discovered by 

 Lowell are just those to be expected on a planet which is 

 like a cryophorus : a planet which has one side permanently 

 heated — and conseciuently having an inward and upward 

 fountain circulation of atmosphere. 



.Again. G. H. Darwin's "Tidal Theory" suggests the reason 

 for and the probability of Venus always turning the same face 

 to the Sun — which probability is increased by the likelihood 

 that Venus never revolved as fast as the earth did at the time 

 of the birth of the Moon. For Venus has no large satellite. 

 Hence she was never disrupted by the tidal action of the Sun 

 operating in conjunction with centrifugal force, due to very rapid 

 rotation. Vet, since solar tides on Venus are much more potent 

 than on the earth, this disruption is a priori the more likely. 

 If. then, Venus never rotated as fast as the Earth once did, she 

 would the more quickly have been stopped by these same tides ; 

 and having no large satellite, there is no other attractive force 

 to oppose that of the Sun. To sum up, every piece of reliable 

 evidence we have been able to adduce points to a rotation 

 period oi two hundred and twenty-five days. There is not a 

 shred of conflicting testimony. There seems to me to be 

 no reason whatever for hesitating further to accept the indicated 

 conclusion that the orbital and rotational periods of Venus 

 are identical. 



JAMES H. WORTHINGTON. 



LOWF.I.L Observ.atorv. 



Fl.\gst..\i-i-. A.T. 



ORNITHOLOGY. 

 To the Editors of " Knowledge." 



Sirs, — In " Knowledge " for December, I noticed that a 

 correspondent wrote regarding the starling as a mimic ; I 

 write an article headed — "' Does the starling relieve sheep of 

 ticks ? " 



On grounds where sheep are grazing, especially if such 

 grounds be somewhat boggy, starlings are seen perched upon 

 the backs of sheep. Starlings are said to visit sheep in order 

 to feed on the ticks which infest the sheep. After close, 

 patient watching I could never see the starlings pick into the 

 wool on the back of the sheep for ticks. I am inclined to 

 think that the starlings visit sheep because they find their 

 backs comfortable and handy. Then these birds seem to be 

 of a very friendly nature to animals they are accustomed to 

 feed amongst. .\n article in " Nature Notes " of the Scots- 

 man recentlv showed the social nature of this bird in 



captivity with a cat, " Starling and kitten." The bird was 

 seen perched upon the back of the cat. Sometimes the 

 starling was found sleeping in this position for half-an-hour. 



EDGAR GRANT. 



EDLS'BURGH. 



THE VELOCITY () E LKIHT. 

 To the Editors of " Knowledge." 



Sirs, — I am a little disappointed to find that Colonel Gibbs 

 was not facetious in his suggestion as to the velocity of light. 



May I point out that his error is based on his fundamental 

 fallacy that the eye " is not capable of seeing anything that 

 passes across its field of vision in less than a tenth of a second." 

 This may or may not be true of some objects — such as a 

 bullet — -but it is absurd to suppose it true of a luminous 

 object. 



CHARLES E. HENHAM. 



Colchester. 



THUNDERSTORMS. 



To the Editors of " Knowledge." 



Sirs, — Mr. Chamberlayne asks in your issue of Jaimary 

 last : — " Inasmuch as the world is round and thunderstorms 

 like everything else have a beginning, it follows that the first 

 flash of lightning in any storm must be directly over some- 

 body's head. How is it then that we cannot meet with 

 anyone who remembers anything of the sort ? " 



My estimate based on observations here would be that out 

 of one hundred thunderstorms one breaks almost exactly 

 overhead. .A remarkable case occurred here about six weeks 

 ago ; remarkable because the discharge came to the ground, 

 which is unusual at the very beginning of a storm ; and it 

 was so heavy that it injured telephones. 



Tr.\nsv.a.\l Observatory, K. 1'. A. INNES. 



Johannesburg. 



To the Editors of " Knowledge." 



Sirs, — Mr. Chamberlayne's letter on " Thunderstorms " 

 recalls an instance which I may offer as an answer to his 

 question. One afternoon in the late spring of 1892, at Denver, 

 Colorado, the sky clouded slowly, whilst the temperature 

 remained rather high. .At six o'clock the heavens were entirely 

 covered, and half an hour later, without any preliminary 

 electrical display, a brilUant flash of Hghtning rent the clouds, 

 and was followed instantly by a heavy peal of thunder. In a 

 few minutes rain began to fall. The storm, with its attendant 

 electricity, lasted nearly an hour before moving away. 



This is the only instance of the kind that I have particularly 

 remarked. Here, on the coast of California, thuiulerstorms, 

 even of a mild type, are infrecjuent, so there is little opportunity 

 to make observations of their phenomena. Storms in the 

 mountains are sometimes visible here, at a distance of from 

 fifteen to twenty-five miles, and, as these are always local in 

 character, the " first flash direcily overhead " must often have 

 been observed in them. 



CHARLES C. CONROY. 



Los .Angeles, 



Califoknia. 



NOTICES. 



THE HORNIMAN MUSEUM. -The new Library at the 

 Horniman Museum, which was recently opened to the public, 

 will now be available on week days throughout the year, from 

 U,0 a.in.to 9.0 p.m., and on, Sundays from 3.0 to 9.0 p.m. It 

 will, however, be closed on Christmas Day, Good Friday and 

 Bank Holidavs. 



FLAME CARBONS.— Messrs. William Gniper and 

 Company, have introduced improvements in their flame 

 carbons, with the result that their business in this depart- 

 ment, as in others, shows considerable increase upon that of 

 1910, or indeed of any year since they took over the business 

 of Messrs. Paterson and Company. 



