604 



NATURE 



[January 27, 19 16 



<;ontributions to medical literature, among them being 

 a treatise in four volumes on the pathology of the 

 heart and aorta; clinical lectures on malaria; sub- 

 continuous fevers, containing his earliest researches on 

 malaria ; and State medicine and clinical medicine in 

 ancient and modern Rome. 



RESEARCH IN TERRESTRIAL 

 MAGNETISM.^ 



THE handsomely printed and illustrated volume 

 before us records the activity of the Department 

 of Terrestrial Magnetism by land from 1911 to 1913. 

 In pp. 5-20 we have an account, illustrated in plates 

 .2, 3, and 4, of instruments used in the world survey 

 on which the department has been engaged since 1905. 

 Pp. 21-182 deal with the land observations made 

 during 191 1 to 1913. The names of thirty-four ob- 

 servers are recorded on p. 23. Of the 983 stations 

 •occupied, 207 were in Africa, including 106 in Algeria 

 and the Algerian Sahara, 52 in French West Africa, 

 and 13 in Morocco. In Asia there were 83 stations, 59 

 being in China or Indo-China. There were 284 

 stations in Australasia, and 247 in South America, 

 the latter distributed in eleven countries, 63 stations 

 being in Peru and 52 in Brazil ; 46 stations were occu- 

 pied in islands in the Pacific, Atlantic, and Indian 

 Oceans, and 30 in the Antarctic, by members of Sir 

 Douglas Mawson's Expedition, trained and supplied 

 with instruments by the department. The results are 

 4:abulated on pp. 26-64 of the volume. The following 

 sixty-four pages are devoted to the observers' reports, 

 illustrated by seventeen photographs in plates 5, 6, 

 ■and 7. 



One of the most interesting reports is Mr. D. W. 

 Berky's account of his travels from Algiers to Tim- 

 buktu, which includes varied information as to camels 

 and wild life in the Niger. On several occasions in 

 the Sahara such heavy electrical charges from wind- 

 driven sand appeared on the instruments that observa- 

 tion was impossible. On one occasion half-inch sparks 

 were drawn when the instrument was touched. Another 

 interesting narrative is that of Mr. H. M. W. Ed- 

 monds, who occupied thirty-eight stations, mostly in 

 remote parts of Canada, travelling more than 2000 

 miles by canoe. One of the largest pieces of work was 

 a magnetic survey of Australia carried out by Mr, E. 

 Kidson and three assistants. During 1910 and the 

 first half of 191 1 Mr. W. H. Sligh travelled 22,000 

 miles, commencing observations at Constantinople and 

 finishing up with Helwan. His eighty-four stations 

 included Jerusalem, Jericho, Damascus, Smyrna, Bag- 

 dad, Bombay, Aden, and Suez. Particulars of the 

 several stations occupied by all the observers occupy 

 pp. 130 to 182. 



Pp. 185-200 describe the new headquarters of the 

 •department in Washington, comprising a commodious 

 main building, which cost, without equipment, 68,000 

 dollars, and a standardising observatory of wood. A 

 "high tower is In contemplation for atmospheric elec- 

 tricity. The buildings are shown in plates i, 8, and 9. 

 On pp. 201-209, and in plate 10, the director. Dr. 

 Bauer, deals with a nine-months' trip which he made 

 in 191 1, when he travelled 47,000 miles, visited eighteen 

 magnetic observatories, Including Mauritius, Dehra 

 Dun, Bultenzorg, Chrlstchurch, N.Z., Tsingtau, and 

 Toklo, and observed during a total solar eclipse In 

 Samoa. 



The final section, pp. 211-278, discusses the corn- 

 parisons made since 1905 of the standard magnetic 



1 Re'searches of the Department of Terrestrial Magnetism (Carnegie 

 Institution of Washington'). Vol. ii. Land Magnetic Ohserv»tions, igii-n, 

 and Reports on Special Researches, bv L. A. Bauer, Director, and J. A. 

 Fleming. Chief Magnetician. Pp. 278 + 13 plates. (Washington, D.C.: 

 Carnegie Institution, 1915.) 



NO. 2413, VOL. 96] 



instruments at some thirty observatories, photographs 

 of eighteen of which are shown in plates ii, 12, and 13. 

 In the case of H (horizontal force) it is assumed that 

 the correction to the value observed with a particular 

 Instrument is proportional to the local value of H. 

 This is true when the sole cause is error in the calcu- 

 lated moment of inertia of the magnet. There are, 

 however, other less universal causes of error which 

 may follow different laws. Two ultimate standards 

 are mainly referred to, entitled C.I.W. (Carnegie In- 

 stitution, Washington) and l.M.S. (International Mag- 

 netic Standards). The C.I.W. standard is that to 

 which all the department's land observations from 

 1905-13 have been reduced. It is embodied in a cer- 

 tain magnetometer and dip-inductor, with specific 

 small corrections applied. The l.M.S. standards In D 

 (declination) and H represent a mean from 42 magneto- 

 meters, 22 belonging to the department ; while the 

 l.M.S. standard for I (inclination) represents a mean 

 from 25 dip circles, the majority by Dover, and 18 dip 

 inductors. The differences between the C.I.W. and 

 l.M.S. standards are given as o-i' in D, 05' in I, and 

 0-00015 H in H. The authors think that if suitable pre- 

 cautions are observed the magnetic standards at an ob- 

 servatory should maintain for a period of five to ten 

 years constancy to within 0-2' in D and I, and 000015 H 

 in H. The comparisons between the C.I.W. standards 

 and those at Potsdam and Kew, " two observatories 

 where . . . every care is bestowed upon instruments 

 and constants," show, it is said, no changes not 

 reasonably assignable to observational errors. The 

 authors add : — " No undue significance is to be at- 

 tached to the circumstance that the corrections for 

 the Washington standards (on the l.M.S. scale) are 

 apparently the smallest of the three observatories." 

 The Washington standard magnetometer is, in fact, 

 believed to give values for H exactly midway between 

 those given by the Kew and Potsdam standards, which 

 are supposed to differ by 16 parts In 100,000. 



The work represents a large amount of accumu- 

 lated experience and will doubtless be widely read by 

 magnetlclans. C. Chree. 



BIRD MIGRATION IN AMERICA.-^ 



THE latest contribution by Mr. W. W. Cooke to 

 the literature on bird migration deals with the 

 general subject, especially in its American aspects, 

 and is of an acceptable and interesting character. To 

 condense into a brochure of forty-seven pages the main 

 conclusions drawn from observations extending over 

 more than twenty-five years, during which 500,000 

 records were communicated by some 2000 observers 

 located In all parts of North America, is an achieve- 

 ment worthy of admiration. 



Written In a lucid manner, It affords useful informa- 

 tion on the many-sided subject on which it treats, 

 among others on the causes of migration ; weather 

 relations ; day and night migrants ; distances travelled ; j 

 routes ; speed ; how birds find their way ; Influence of 

 temperature, etc. In treating of these the author 

 has drawn his conclusions from the movements of a 

 number of typical American migratory birds, 

 and to exemplify them more effectually has 

 introduced a series of maps and diagrams show- 

 ing the summer and winter distribution of each 

 species treated of, migration routes, Isochronal 

 migration lines, etc. These serve, among other pur- 

 poses, to illustrate Mr. Cooke's conclusions with re- 

 gard to the routes taken by the migrants when cross- 

 ing the Gulf of Mexico, showing that by far the 

 greatest number of migrants choose the shortest route 



1 " Bird Migration." By Welh W. Cooke, Un ted States Department of 

 Agriculture. Bulletin No. 185. (Washington, D.C., 1915.) Price 10 cents. 



