362 



NA TURE 



\_Feb. 17, 1 88 1 



The questions whether a geolojjical period is to be classified as 

 liitherto it always has been classified, by an appeal to zoology or 

 by an appeal to ice, and whether the naturalists who have de- 

 voted themselves to the study of mammalia have only "opinions," 

 while Dr. James Geikie enjoys "the facts," may be left in 

 silence to the judgment of geologists. In the review under 

 discussion all reference to my own opinion and works has been 

 carefully omitted. Here, so far as I am concerned, the discus- 

 sion ends. W. Boyd Dawkins 



Owens College, February 1 1 



Geological Climates 



In Nature, vol. xxiii. p. 241, Dr. Ilaughton repeats his 

 former statement that "it is imposible to suggest any rearrange- 

 ment of land and water wliich shall sensibly depress the tempera- 

 ture of the east of North America." Now we must only look 

 about us to see that the east of Asia is colder than the east of 

 North America, parallel for parallel, and this especially in 

 winter. The mean temperature of January is as follows iu 

 places situated as far as possible under the same latitude and at 

 the same distance from the sea : — 



This shows that (l) from lat. 20° to 55°, Eastern Asia is every- 

 where from 7>,° to 19' F. colder in January than Eastern North 

 America ; and that (2) thee parts of the coast of Eastern Asia 

 which are not separated by mountains from the interior lowlan Is 

 are much colder than those which are sheltered, but even the 

 latter parts, though relatively warmer, are yet much colder than 

 the same latitudes in Eas.ern North America. These differences 

 are explained by geographical position. Asia is the larger con 

 tinent; its ea-tem interior is more secluded from the influences 

 of warmer seas, and its eastern coast more subject to Continental 

 influences, and thus colder in winter than North America. We 

 thus see by the example of Asia that a colder tem erature than 

 in Eastern North America does really exist now in the same lati- 

 tudes. The example of Eastern A~ia shows us geographical 

 conditions which tend to produce an exceedingly cold winter. 

 We have but to look at the middle and higher latitudes of the 

 southern hemisphere to see so cold summers that nothing of 

 the kind is met with in the northern. I do not know on what 

 authority Dr. Haughton slates that the annual temperatiu-e of 

 32° F. is met in the southern hemisphere but on 62° 41' S. We 

 do not haveob.-ervations durini the winter in these latitudes', but 

 the mean temperature of January (the warmest month) is found 

 to be 352 on 60° S. and 32-4 on 634° S. Or (by the observations 

 of Sir J. Ross) the mean annual temperature can certainly not 

 be less than 4^° below that of January, so that it would be not 

 higher than 307 on the 60° S., and 27-9 on the 63^° S. 



St. Tetersburg, February 5 A. WoEIKOFF 



Variable Stars 



With reference to your remarks on variable stars in the 

 Astronomical Column of Nature, vol. xxiii. p. 2o5, I beg to 

 send a few observations made by me (on some of the stars 

 referred to) during the past few years : — 



5. 35 Camelopardi. October 1875. I found this star about 

 6J m. and fainter than (27 Fl.). — October 6, 1879. 7 mag. ; 

 about I mag. less than 0. 



6. Riimker's star. I have the following observations : March 

 27. 1875. About 7 m.; fainter than 25 Monocerotis. — January 

 19, 1S76. 65 m. ; less than 25, but brighter than two 7 m. stars 

 s.f. it.— Mai-ch iS, 1877. Distinctly visible to the naked eye ; 

 abiut 6m., but less than 25 (5.6m. Heis). The above ob.serva- 

 tions were made in the Punjab. 



7. 65 (5- Geminorum. December i, 1880. 65 so exactly equal 

 to 64 Geuiinorum with ojiera glass that I could see no difference 

 between them in magjiitude. 



' Nearly one degree to the North of Victoria. 



8. 16 Leonis Minoris. March 27, 1875. About 7im. — 

 January 19, 1876. 7-3 or 7"Sm. 



10. Lalan le 38405. August 31, 1877, I found this star fainter 

 than Lalande 3S38S, which lies about 20' north of it ; also less 

 than a 6 m. Harding (Lalande 3S214) s.p. it. Brighter than 

 Lalaade 38342 (7^, 8), which lies n.p. it. 



11. 33 Capricorni. August 1875 I estimated this star as 6J m. ; 

 August 1876, 6 m., and slightly brighter than 35 Capricorni. 



12. I (17) Andromed*. From numerous observations, be- 

 ginning in May 1875, I have detected a variation in the light of 

 this star to the extent of about half a magnitude. It is sometimes 

 distinctly brighter than k Andromedee, and sometimes decidedly 

 fainter. 



With reference to i8 and 5 Scorpii I find the following obser- 

 v.ation in my note-b3ok : — 



"Punjab, August 10, 1876. /3 Scorpii (2m. Heis) and 8 

 Scorpii (2'3m. Heis) almost exactly equal. Perhaps S, if any 

 thing, very slightly the brighter of the two. J. E. Gore 



Ballisodare, Co. Sligo, Ireland, February 5 



The Mode of Flight of the Albatross 



There seems to be a prevailing idea that the albatross in his 

 flight is in some way "assisted by the wind." I think this is a 

 mistake ; the manner is well known. The method I believe 

 admits of a very simple explanation. His secret consists in his 

 power of acquirin.; great momentum together with the large 

 superficial area of his extended wings ; with scarcely a motion of 

 his wings he w ill fly straight against a strong wind with a velocity 

 greater than that of any racehorse ; this is inconsistent with the 

 idea of his being "assisted by the wind." 



In attempting to rise from the water (I believe he is unable to 

 rise from the land or from a ship's deck) he flaps his wings 

 violently to get his body out of the water ; at the same time, 

 paddling rapidly with his webbed feet, he acquires a moderate 

 de^jree of momentum, sufficient, with outstretched wings, to carry 

 him forward and upward upon an easy incline. The case is 

 similar to that of a boy taking a run with hi-^ kite string in his 

 hand to give his kite a start. During this first rise he will gene- 

 rally give a few heavy, lazy flaps, and then stretch his wings 

 steaddy to their full extent ; now as he gradually rises he must 

 of course as gradually lose his acquired momentum till it suits 

 him to acquire m ire, when he may be twenty, thirty, or fifty 

 feet above the surface, but a much greater distance from the 

 place where he left the water, measured on the surface ; by 

 slightly altering his position, by a movement of his tail, he takes 

 a shoot downwards at any angle that suits his convenience, still 

 without his wings outstretched. This is preci^elythe case of a boy 

 shooting down a coast on his sled ; the propelling force is the 

 same. The bird directs his course mainly with his tail, the 

 action of which upon the air is identical with the action of a 

 ship's radder upon the water. By this downward motion, his 

 velocity rapidly increasing, he acquires a degree of momentum 

 sufficient to cirry him up again to a height equal to or greater 

 than that from which he started. In this up and down long 

 wave-like motion, with all its variations on either side, consists 

 the whole of his flight day after day for hundreds of miles ; at 

 long irregular intervals he may give a few lazy flaps with his 

 immense wings. Other birds use the mode of flight of the 

 albatross, but to a smaller extent, for the reason, in the case of 

 smaller birds that, the ratio of feathers to bulk being greater, 

 their specific gravity is less, consequently they are unable to 

 acquire the degree of m omentum necessary to carry them upward ; 

 but on the other hand they have the power of sustained effort in 

 moving their wings rapidly, which the albatross has not. Gravi- 

 tation then, which prevents him from rising directly on the wing, 

 is the motive power of the albatross when aloft. He must always 

 take a run or paddle over the surface of the water in order to 

 get a start, and on the land or the deck he is a prisoner, because 

 he has no water in which to paddle himself along with hi^ webbed 

 feet, and he is unable to run. Instead of being assisted by the 

 wind, his speed is lessened by just so much as the wind's velo- 

 city, when it happens that the direction of the ^\ind and his 

 intended course are opposed to each other, but with the wind 

 his speed is just so much greater than it would be in a calm. 



I do not advance this explanation as an imaginative theory. 

 I claim more for it. I have had many opportunities of studying 

 the movements of the albatross for consecutive days, and I feel 

 confident that the above will be found to answer all requu-ed 

 conditions. Howard Sargent 



Cambridge, U.S. 



