CORRESPOXDEXXE. 



THE FLICHT OF THE ALBATROSS. 

 To the Editors of " Knowlkdge." 



Sirs, — We often hear of the mystery of how the Albatross 

 can fly without flapping its wings. I have often by the hour 

 closely watched these birds on the wing, and seen that they 

 make no movement save slight guiding and directing altera- 

 tions of tail and wing. The head is moved about freely to 

 look in all directions, and the bird will occasionally scratch 

 itself with claw or beak, for they always swarm with \ermin, 

 but usually there is no flapping of the wings at all. 



In these days of fast steamers, as there are few opportunities 

 of watching their flight, may I record my evidence of how one 

 of these birds will thus follow a ship for many days and nights 

 together ? 



First, they only fly in their characteristic manner while the 

 wind is blowing. As the wind drops they begin to flap : and 

 as a calm comes on they soon tire of flying by flapping and 

 settle on the sea like great ducks. Then when enough wind 

 remains to move the ship they are usually left behind and not 

 seen again. Why they so soon tire of flapping is because the 

 humerus (arm-bone) is very long, while the pectoral muscles 

 are comparatively small and supported by a small keel to the 

 sternum. 



Presumably they use the wind to help them to fly. But 

 how ? 



All the while they are flying they are repeatedly rising high 

 into the air, then swooping down close to the sea surface, and 

 then up again. If there was no friction nor other loss of 

 energy, the impetus of the swoop would enable the creature to 

 rise to as high a spot as it came down from. Or if it could 

 get from the wind a little impetus to replace the certain loss of 

 energy the bird could continue to rise and fall as long as the 

 wind blew. It does this. 



W'hen there is wind at sea there are also waves. .As the 

 wind slides up the back of a wave towards the crest it is 

 directed upwards. The .\lbatross always swoops deep into 

 the trough of the sea, where it is somewhat sheltered from the 

 wind, and there, facing towards the on-coming wave, it begins 

 to rise close to the front surface of the wave. When it 

 crosses the crest the bird may be seen to get a distinct " lift " 

 from the up-current of air. 



To fly by this method across the wind, or in the direction of 

 the wind, the .-Mbatross has to make curious gyrations, so as to 

 face the wind after each swoop. If this manoeuvre is pre- 

 vented, as by the distraction of some tit-bit or a quarrel with a 

 companion, the bird has to flap and fly like any other gull. 



This mystery is as usual made by omitting a necessary 

 detail of description ; as also w-hen we are told that often 

 when placed on deck this sea-bird is sea-sick I It we were 

 told that while it was being hauled on board the bird had 

 gaped its beak wide open to get the hook out, and being 

 dragged through the crests of several waves it had thus 

 swallowed large quantities of sea water, then we should guess 

 that it was sick from sea water, not from the motion of the 

 ship. 



How the Albatross can do without sleep for so long remains 

 a mystery. It sometimes looks half asleep while it executes 

 its monotonous movements, ^ Ao,-rr T^r-t-i-e 



ROTATION ol- VEXUS, 



To the Editors of " Knowledge," 



Sirs, — The April Number of " Knowlkdgk " contained a 

 short article of mine on the above subject, in which I advanced 

 some reasons for assuming that \'enus still has a rotation 

 period shorter than its year, even though this rotation might 

 be too slow to be detected from observation. It is interesting 

 to learn that since then M, Belopolsky has confirmed some of 



his previous spectroscopic work, giving the planet a period of 

 1 ■ 44 days. This result is in accord with theory, and corrob- 

 orates to a great extent the early observations of Schroter 

 and De ^'ico, On the other hand Mr, Slipher has obtained 

 no indication of a rapid rotation from the spectrum of Venus, 

 which agrees with the direct visual work of Schiaparelli and 

 Lowell. 



These conflicting observations of experienced astronomers 

 are very unsatisfactory, and are the more extraordinary as 

 each result has been confirmed by an independent method of 

 research. We can only hope that ere long some decisive 

 evidence may be obtained upon this, at present, baffling 



'l"<^st'"n- B. G, HARRISON, 



CLUSTERS AND NEBULAE. 

 To the Editors of " Knowleuge," 



Sirs, — Referring to my article " Clusters and Nebulae'' in 

 vour September number. I have just received a letter from Dr. 

 Fath. of the Mount Wilson Solar Observatory, Pasadena, 

 California, together with a minute print of one of his Lick 

 Spectrograms of the .Andromeda Nebula. Notwithstanding 

 its small scale there appear to be indications of lines corres- 

 ponding to those in the solar spectrum, and he states there are 

 other fainter lines (lost in the print). 



I am accordingly sending you this note at his desire, so that 

 it may be seen that his opinion (quoted on page 344, column 1) 

 was not given without evidence. Dr. Fath also states in his 

 letter "Dr. Lockyer and Mr. Frank McClean were here a 

 few months ago, and saw some of the original negatives, I 

 believe they will agree that these absorption lines are well 

 marked in the originals," p -ly hENKEL 



THE VELOCITY OF LIGHT. 



To the Editors of " Knowledge," 



Sirs, — Surely your correspondent, G. R. Gibbs. is trying to 

 hoax your readers with his suggestion that light has its velocity 

 reduced by the earth's atmosphere to some twenty miles a 

 second because he can see a flash of lightning. Considering 

 that he admits that the observations for computing the velocity 

 of light actually showed a velocity of one hundred and eight\- 

 six thousand miles a second near the earth's surface, it is 

 difficult to see on what principle of logic he yet considers that 

 twenty miles is the correct figure. Does he really imagine that 

 a brilliant spark will become invisible if it takes less than 

 one-tenth of a second to accomplish its path ? Considering 

 that the spark of an electric machine is visible when one-tenth 

 of an inch long, are we to infer that such sparks only travel 

 one mch in a second ? CH-^RLES E, BENHAM. 



To the Editors of " Knowledge," 



Sirs. — Theosophists state that the Earth has a motion which 

 has not yet been discovered by Astronomers, 



This motion consists of the rotation of the Earth's axis 

 about its centre thereby causing the Earth to " turn turtle " as 

 the saying is, in other words that in time the Southern 

 Hemisphere will face the Pole star in a similar manner that 

 the Northern Hemisphere does at present. 



If this statement is correct it would fully account for the 

 various large changes in temperature which appear to ha\e 

 taken place in the different parts of the Earth, 



Does not the dift'erence in the inclinations of the axes of the 

 pl.uiets to the planes of their orbits point to the possibility of 

 all the planets being subject to this motion ? 



F. G. STOPFORD (Admiral). 



471 



