234 



NA TURE 



[January 5, 1899 



hi.niannes I'ri/e (2coo (r.) for researches in pal.vontology. In 

 Biology, the Grand Prix of the Physical Sciences (3000 fr.) for 

 a sliKly ol the biology of Nematods, especially (he forms and 

 conditions of their reproduction, and the Bordin Prize (3000 fr.). 

 In Botany, the Desmazicres Prize (1600 fr.) for work on the 

 Cryptogams; the Montagne Prizes (1000 fr. and 500 fr.) for 

 important work bearing on the anatomy, physiology, develop- 

 ment, or description of the lower Cryptogams ; and the 

 Thore Prize (200 fr. ) for the best memoir on the cellular 

 Cryptogams of Europe. In Anatomy and Zoology, the 

 Savigny Prize (975 fr. ) for the assistance of young 

 travelling zoologists. In Medicine and Surgery, a Montyon 

 Prize for discoveries or inventions having a direct bearing upon 

 the art of healing ; the Barbier Prize (2000 fr. ) for similar 

 objects; the Breant Prize ( 100.000 fr.) for the discovery of an 

 absolute specific against Asiatic cholera : the (Jodard Prize 

 (1000 fr.) for the best memoir on the anatomy, physiology, and 

 pathology of the genito-urinary organs ; the Serres Prize for a 

 memoir on general embryology applied as far as possible to 

 Physiology and Medicine ; the Chaussier Prize (10,000 fr.) for 

 the best book or memoir which has appeared during the last 

 four years, either in medicine, legal or practical medicine ; the 

 Bellion Prize (1400 fr.) ; the Mege Prize (300 fr.); the Lalle- 

 mand Prize (1800 fr.) for work on the nervous system ; and the 

 Baron Larrey Prize (1000 fr. ) for a memoir on military or naval 

 medicine, surgery, or hygiene. In Physiology, a Montyon 

 Prize (750 fr.); a La Caze Prize (10,000 fr.): the Pourat 

 Prize (1400 fr. ) for a memoir on the specific characters 

 of the contraction of different muscles ; and the Phili- 

 peaux Prize (890 fr. ) for work in experimental physiology. 

 In Physical Geography, the Gay Prize (2500 fr. ) for a study of 

 the Mediterranean mollusca, and a comparison of these with 

 those found on the P'rench oceanic coasts. 



Other general prizes offered for 1S99 include the Arago 

 Medal, the Montyon Prize (unhealthy trades), the Tremont 

 Prize (lioofr.), the Gegner Prize (4000 fr.), the Petit D'Ormoy 

 Prizes (10,000 fr. each), one for work done in mathematics, 

 and the other in natural science ; the Leconte Prize 

 (50,000 fr. ), the Tchihatchef Prize (3000 fr. ), the Gaston 

 Planie Prize (3000 fr. ), the HouUevigue Prize (500 fr. ), the 

 Wilde Prize (4000 fr. ), the Saintour Prize (3000 fr.), the 

 Kastncr-Boursault Prize (2000 fr.), the Jean Jacques Berger 

 Prize (12,000 fr. ), and the Baron Joest Prize (2000 fr. ). 



Of these the prizes bearing the names of Wilde, Tchihatchef, 

 Leconte, Desmazicres. Delesse, La Caze, and Lalande are 

 expressly stated to be offered without distinction of nationality. 



MAGNETIC SURVEYS.^ 

 'TTHE importance of magnetic survey work has been recognised 

 ■*• for a long time. Many of the most eminent scientific men 

 of the century now about to close have devoted much time and 

 thought to magnetic observation and the reduction of results, 

 and their labours have not been without fruit. To them we owe 

 all that is known with certainty as to the magnetic state of the 

 earth and its changes ; and though observations have no doubt 

 to .some Uagree outpaced the work of reduction and the con- 

 struction of theory, much has been done to construct from ob- 

 servational data a general theory of terrestrial magnetism. We 

 have the great mathematical theory of Gauss based on the re- 

 sults of Sabine, Barlow, Horner, and others, with the answer it 

 g:ives to the question of the locality of the magnetic distribution 

 which gives rise to the ordinary phenomena of terrestrial mag- 

 netism. Also, and founded to .some extent on (iauss's theory, we 

 have now that of Schuster on the daily changes of the magnetic 

 forces and their causes, which has yielded most important re- 

 sults, as to the locality of the sources of this periodic disturb- 

 ance. .■\s a consequence of Schuster's theory there have lately 

 been published some important discussions of the diurnal 

 changes and their theory by von Bezold and others. 



The secular changes have received a great accession of interest 

 since Bauer's first discussion of the subject some years ago in an 

 inaugural dissertation at the University of Berlin. In that he gave 

 the method of graphical representation of the secular changes now 

 known by his name. An observer is supposetl to look from the 



1 " .Vlaryl.ind GeoloRical Survey. First Report upon Magnetic Work in 

 Maryland, including the History and ObjectMif M.aKnetic Survevs." Bv 

 I.. .\. Hauer. Sp-cial Ptihlicalio", Vol. I , Part \-. Pp. v + u,, will, one 

 lih.f: (Hallimorc : The Johns Hopkins Press, .897.) 



NO. 1523, VOL. 59] 



centre of a magnel, freely .suspended at its centre of gravity, and to 

 note the curve which the north-pointing pole seems to describe, 

 and which shows changes of dip as well as changes of magnetic 

 declination. This mode of representation can, of course, be 

 applied to the diurnal changes, and shows that though a com- 

 plete cycle of secular changes is not yet available from observ- 

 ations, yet the diagram of the diurnal changes may serve to 

 complete it. Let the secular changes be produced by the 

 combination with a constant magnetic system rotating wiih the 

 earth of a second system, also turning with the earlh, but 

 \\hile doing so describing a secular orbit round the earth's 

 axis. This is the hypothesis of Wilde. Now let a needle be 

 imagined suspended out.side the earth while the earth turns 

 beneath it. The superimposed magnetic .system will in the 

 course of one rotation of the earth occupy the same position 

 relatively to the suspended needle that it successively occupies 

 in the secular period with reference to a needle fixed with the 

 earth and turning with it. The curve thus obtained for a single 

 day will, if the second system be invariable and its successive 

 po.sitions be symmetrical about the earth's axis, be the same as 

 the secular curve. Thcugh this curve cannot be directly ob- 

 served, for no needle can be suspended in the manner supposed, 

 the distribution of magnetic force round the earth is sufficiently 

 well known to enable the positions of the needle to be calculated 

 and the curve laid down on paper. The indications at the same 

 instant of time of needles suspended at dift'erent points of the 

 same astronomical circle of latitude, in fact, give the curve. 

 There is sufficient .similarity between the curves obtained in this 

 way ' to afl'ord a fairly satisfactory first test of Wilde's hypothesis, 

 anti no doubt further progress in the solutii>n of this interesting 

 question will shjrtly be obtained by Dr. Bauer himself, or 

 others. 



The origin of the diurnal and secular variations may perhaps 

 become known fully only when the secret of terrestrial magnet- 

 ism itself is revealed. In the meantime there can be no question 

 of the absorbing interest of the problem, and of the fact that the 

 only way to solve it is by means of continued magnetic observ- 

 ation at different parts of the world, at sufficiently equipped and 

 properly chosen magnetic observatories. It i- to be hoped 

 that as the value of observations, so far as the secular changes 

 are concerned, depends on their comparison with those 

 obtained much later in time, care will be taken in future by 

 municipal and government authorities not to injure or render 

 nugatory the work done by bringing disturbing electric currents 

 and traffic into the vicinity of observatories. The fact that a 

 sub-section (of Section A) of the British .Association gave itself 

 at the recent meeting to the discussion of terrestrial magnetic 

 problems is at once an indication of fuller recognition of the 

 interesting nature and the importance of magnetic research, and 

 a guarantee that magnetic observatories and laboratories will be 

 made to co-operate to the best advantage in the work to be 

 done, and that everything will be done to induce authorities to 

 protect them when powers are being sought for engineering 

 projects. 



Dr. Bauer has .set before us a brief but interesting state- 

 ment of the history of magnetic research, the objects to be served 

 by it, the kind of .survey work that may be attempted best by 

 observers in diflferent localities, and the mode in which it should 

 be carried out, illustrated by an .account of a survey of part of 

 the State of Maryland which he has lately undertaken. 



There are many notes of great interest in this historical 

 sketch. l'"or example we find, what we confess we did not 

 know before, that the discoverer of the declination of the 

 compass needle from the true north was Christopher Columbus. 

 It seems that on September 13, 1492, Columbus crossed the 

 agonic line, the line of no declination, a little to the west of 

 the Lsland of I>'.ayal in the Azores, and observed that the 

 compass at places cm the east of this line pointed east, and at 

 places on the west pointed west of the true north. This line 

 ran, curiously 'enough, along the old boundary between the 

 kingdoms of Portugal and Castile. Generally Columbus has 

 received credit only for discovering the agonic line, owing to a 

 statement of Kormaleoni, the Italian historian, that Bianco's 

 chart of 1436 contained values of the declination, an error which 

 Humboldt perpetuated by repeating in his " Cosmos." The 

 recorded value of the magnetic declination at Rome in 1269, 

 ascribed to Petrus Peregrinus, was inserted, it appears, by some 

 one early in the sixteenth century, thus subsequent loColumbus. 



That the declination had not been discovered sooner arose 



Sec Prof. Rii.ke 



liber 13, i8i)7. 



