March 8, 1889.] 



SCIENCE. 



187 



•shedding new light on this most important topic. The editor of 

 the Revue, M. Ch. Richet, the well-known physiologist and psy- 

 <;hologist, requests that all who have facts to present will send them 

 to him. His address is iii Boulevard Saint-Germain, Paris, 

 France. 



— Harper & Brothers have just ready " The Correspondence of 

 John Lothrop Motley," edited by George William Curtis. Mr. 

 Motley's daughters have collected these letters, chiefly addressed to 

 the writer's family and to Oliver Wendell Holmes. They contain 

 the autobiography of one of the most striking figures in Ameri- 

 can literary history. The author of " The Rise of the Dutch Re- 

 public," " History of the United Netherlands," and " The Life 

 and Death of John of Barneveld," studied the history of liberty in 

 an essentially American spirit. Wendell Phillips was his school 

 chum, Bismarck his fellow-student at Gottingen ; and as United 

 States minister to London, Holland, and Austria, he made personal 

 friends of all the literary and political celebrities of his day. Few 

 lives have been so full of incident of universal interest. The work 

 is in two volumes, and has a portrait. 



— The Leonard Scott Publication Company (New York, 29 Park 

 Row) has reprinted the famous Bismarck Dynasty article from the 

 'Contemporary Review for February (price 1 5 cents), a large spe- 

 cial edition of that number having been exhausted on the day of 

 publication. The authorship of the article continues to be the 

 theme of much speculation in England. The Empress Frederick 

 has thought it necessary to disclaim it, and so has Sir Morell Mac- 

 kenzie. Many of those who claim to know, attribute it to Mr. 

 Stead, the editor of the Pall Mall Gazette. Mr. Labouchere says 

 he almost knows it was Mr. Stead, and sundry characteristics can 

 be pointed out which lend color to this view. In the mean time 

 €ight editions of the Review have been called for in England. 



— A novel feature in magazine literature was introduced in the 

 Nineteenth Century for February. The editor has invited a num- 

 ber of his friends to send him from time to time, in the shape of 

 letters to himself, remarks upon any books which in the ordinary 

 and natural course of their reading may strike them as being worth 

 special attention. He has suggested to them, that, whenever a 

 book is thus met with, a letter about it should be written to him, 

 giving the same advice as to a friend, and in much the same sort of 

 easy fashion. He hopes in this way to obtain fresher and more 

 spontaneous criticism than can possibly be always produced under 

 the prevailing system of " noticing " books " sent for review." The 

 first instalment of this series consists of a notice of Margaret Lee's 

 novel "Divorce," by Mr. Gladstone; of the "Lyrics," and "A 

 Village Tragedy " by Margaret Woods, by Frederick Harrison ; 

 Dean Burgon's " Lives of Twelve Good Men," by P. E. Prothero ; 

 Sir George Young's " Sophocles," in English, by W. S. Lilly ; 

 "Notes of Conversations with the Duke of Wellington," by Augus- 

 tine Birrell ; Miss Rives's " The Quick or the Dead ? " and " Vir- 

 ginia of Virginia," by Hamilton Aide ; M. Jusserand's " Wayfaring 

 Life," by the Rev. Dr. Jessopp ; and George Pellew's " In Castle 

 and Cabin," by John Morley. 



— The New England Publishing Company have -just published 

 " One Hundred Lessons in Composition," by W. H. Huston of 

 Toronto, which contains 400 practical exercises in composition, and 

 is the sixth volume in their library of Teachers' Help Manuals. It 

 will shortly be followed by " Manual of Rhymes, Selections, and 

 Phrases," by Oscar Fay Adams ; " Forty Friday Afternoons," by 

 forty prominent masters, each giving what he considered his best 

 exercises for a Friday afternoon ; and " Common-Sense Exercises 

 ill Geography," a book of exercises — not questions — adapted to 

 all grades and to the best American text-books. They have also 

 just ready " School Music," by W. S. Tilden, of the State Normal 

 School, Framingham, Mass., a series of papers from the Americatt 

 Teacher. 



— The Critic observed the seventieth anniversary of the birth of 

 Mr. Lowell, which occurred on Feb. 22, by printing seventy letters and 

 poems from American and English men and women of letters, among 

 whom are Tennyson, Whittier, Gladstone, Holmes, and Stedman. 



— Mrs. Frank Leslie has sold to W. J. Arkell, of Judge, her 

 J^rank Leslie's Illustrated Newspaper, both English and German, 



the transfers to be made May i. Mrs. Leslie will retain and per- 

 sonally direct her other publications. 



— Emin Pacha forms the subject of a paper by Elbridge S. 

 Brooks in the February Wide Awake. 



LETTERS TO THE EDITOR. 



*,,* Correspondents are retjuested to he as brie/ as possible. The writer's name is 

 in allcases required as proof of s:ood faith. 



The editor will be ^lad to fiiiblisk any queries consonant with the character 0/ 

 the journal. 



The Soaring of Birds 



May I ask space for a few comments on Professor W. H. Pick- 

 ering's letter on the above subject, in Science of Feb. 22 } 



Professor Pickering holds that a bird which is moving with mo- 

 tionless wings in a horizontal wind is acted upon by three forces : 

 (l) its weight ; (2) a force " due to the excess of the velocity of the 

 wind over the velocity of the bird," by which, since it is repre- 

 sented as horizontal and to leeward in his diagram, I suppose he 

 means the friction between bird and wind ; and (3) a force " due to 

 the resistance of the air acting on the wings of the bird," which I 

 cake to mean the force derived from the impact of the air particles 

 on the wings. This third force he assumes to have a direction 

 opposite to that of the resultant of forces (i) and (2), and therefore 

 to have one component vertically upward, and another to windward. 

 This assumption seems to me to be erroneous. The horizontal 

 component of such a force must surely be to leeward, as was 

 pointed out by Hubert Airy in Nature, xxvii. p. 336 ; and the in- 

 accuracy of this fundamental assumption of Professor Pickering 

 would seem to invalidate his whole argument. 



But let us follow it further. Force (3), he says, depends on the 

 velocities of bird and wind, and he assumes first that these veloci- 

 ties are such that it is equal to the resultant of forces (i) and (2). 

 In that case he says the forces acting on the bird will be in equi- 

 librium. They would be, certainly, if the above assumption were 

 true. " The bird," he then says, " will therefore continue to re- 

 volve about its mean position." How can a body which is in equi- 

 Ubrium revolve about a mean position ? It must surely move with 

 a uniform velocity in a straight line. He says again, " While these 

 forces are in equilibrium, the bird is slowly drifting in the same 

 direction as the wind." Why so ? If the bird is in equilibrium, he 

 must have the same velocity as he had at the instant at which he 

 came to be in equilibrium, and that may or may not have had the 

 same direction as the wind. In fact, if it is true, as Professor 

 Pickering assumes, that the forces acting on the bird can be in 

 equilibrium, the bird can move to any distance, in any direction 

 whatever, with motionless wings. He has but to get up a velocity 

 in the desired direction by using his wings, and then to poise his 

 wings so that the forces acting on him may be in equilibrium. 

 Since this result is contrary to experience, it makes the possibility 

 of the bird's being in equilibrium under the given conditions doubt- 

 ful ; and it is obvious, that if force (3) has a leeward component, 

 as I hold it must, its being equal to the resultant of (i) and (2) 

 does not involve the vanishing of the resultant of all three ; indeed, 

 that whatever assumption may be made as to the magnitude of (3), 

 the resultant of (i), (2), and (3) cannot possibly be zero. 



Finally, Professor Pickering assumes the velocities of wind and 

 bird to be such as to make force (3) greater than the resultant of 

 (l) and (2). In that case, if the assumption criticised above were 

 correct, the bird would be acted upon by a resultant force directed 

 upwards and to windward, as Professor Pickering states. But if 

 force (3) is directed upwards and to leeward, it will be obvious that 

 the resultant force on the bird will be necessarily directed to leeward, 

 and will not necessarily be directed upwards ; and it follows, that, 

 even if the velocities of wind and bird be assumed to be such that 

 force (3) is greater than the resultant of (i) and (2), the bird's path 

 will not necessarily have a general upward direction. 



J. G. MacGregor. 



Dalhousie College, Halifax, N.S., Feb. 27. 



A New Departure in Effigy Mounds. 

 It was first asserted by Dr. J. M. De Hart that there are to be 

 found exceptions to the ordinary rule followed by the mound- 

 builders in the outlines of their quadruped animals ; i.e., that in- 



