Astronomy. 411 



describe as made of drifted sands, and which contrast strikingly 

 with facts in the Central Pacific, are explained by reference to 

 the positions of the areas within the cyclone belt of the ocean. 

 A copy of the map of these regions by the Hydrographic depart- 

 ment, making Plate xr, Li'ives all the soundings of the adjoining 

 The l<nir new colored plates, one representing Actiniae, 

 and the others, species of living corals, are from the author's 

 Zoophyte Atlas. 



IV. Astronomy. 



1. The Diurnal Variation of Terrestrial Magnetism ; by 

 Arthub S( iu'ster. — Prof. Schuster, in a memoir read before the 

 Royal Philosophical Society of London, has discussed the Diurnal 

 Variation of Terrestrial Magnetism, by the methods of Spherical 

 Harmonics. For this he has used the observations for 1870 made 

 at four stations, Greenwich, Lisbon, St. Petersburg and Bombay. 

 He thus sums up the principal results obtained in his paper: — 



(1.) The principal part of the diurnal variation is due to causes 

 outside the Earth's surface, and probably to electric currents in 

 our atmosphere. 



(2.) Currents are induced in the Earth by the diurnal variation 

 which produce a sensible effect chiefly in reducing the amplitude 

 of the vertical component and increasing the amplitude of the 

 horizontal component. 



(3.) As regards the currents induced by the diurnal variation, 

 the Earth does not behave as a uniformly-conducting sphere, but 

 the upper layers must conduct less than the inner layers. 



(4.) The horizontal movements in the atmosphere which must 

 accompany a tidal action of the Sun or Moon, or any periodic varia- 

 tion of the barometer such as is actually observed, would produce 

 electric currents in the atmosphere having magnetic effects similar 

 in character to the observed daily variation. 



(5.) If the variation is actually produced by the suggested cause, 

 the atmosphere must be in that sensitive state in which, according 

 to the author's experiments, there is no lower limit to the electro- 

 motive force producing a current. 



2. Bibliographie Generate cle V Astronomie ; by J. C. Hou- 

 zeau and A. Lancaster. — The second volume of this large and 

 very valuable Bibliography appeared several years ago (see this 

 Journal, vol. xxi, p. 253, and vol. xxiv, p. 76). Two parts of vol. 

 i have since been issued, the first in 1887, and the second in 1889. 

 The first part contains an extended history of Astronomy (325 

 pages) by M. Houzeau. The history of the science in its earlier 

 developments is more particularly dwelt upon. The remainder 

 of this part is given to the Bibliography of the History of As- 

 tronomy and to Astrological Books. There are of these 5415 

 entries. A large number of these are manuscripts. When 

 there are second editions, or translations, or detailed reviews of 

 printed books, the titles of or references to them follow the first 

 entry. 



