168 



NATURE 



[April 7, 1910 



of this specimen, which is of rudely quadrangular form, 

 with a maximum diameter of about 2 J inches, consists in 

 the fact that it was actually seen to fall by the late Mr. 

 B. F. Wilson 6n October 15, 1888, in McDuffie County, 

 Georgia. It fell within a distance of about thirty yards 

 of the observer, who was engaged at the time in picking 

 cotton, and was at first under the impression that some- 

 one had thrown a stone at him. The meteorite buried 

 itself to a depth of some 6 or 8 inches in the soil. 



An application of the hydrodynamical theory of seiches 

 to the Lake of Garda (Benaco) forms the subject of an 

 essay by Dr. Francesco Vercelli {Memorie del R. Istituto 

 Lombardo, vols, xxi.-xxii. [3], i). The form of the lake 

 is very irregular, the lower end being divided into two 

 branches by a rock forming the peninsula of Sirmione, 

 and projecting for a considerable distance further under 

 water. The author has calculated the positions of the 

 various nodes, and has applied Chrystal's so-called 

 " quartic approximation " to determine the periods of the 

 various oscillations. On comparing these with limno- 

 graphical observations made at Desenzano, a good agree- 

 ment has been obtained, while the formulae of Merian and 

 of Du Boys are stated not to have led to the same satis- 

 factory conclusions. 



The ordinary form of liquid bath for the determination 

 of melting points has been modified by the introduction of 

 an airrbubble system, causing a rapid circulation of the 

 liquid, and hence a uniform temperature. The same idea 

 has been very ingeniously applied by Mr. H. Stoltzenberg 

 (Zeitschrift fiir physikalische Chemie, March 11) in design- 

 ing a low-temperature cooling bath. The liquid (pentane) 

 is caused to circulate by means of hydrogen bubbles 

 through a spiral dipped in liquid air, ether, and solid 

 carbon dioxide, or a mixture of ice and salt, according 

 to the temperature required, and then passes into the 

 vacuum-jacketted vessel in which the measurements are 

 carried out. The temperature can be easily regulated by 

 altering the amount of the spiral immersed, and can be 

 kept very constant. 



In the Annalen der Physik, iv., 30 (1909), Dr. M. Laue 

 discusses the question of thermodynamic reversibility as 

 applied to difTraction of light through a grating. The 

 question has assumed a new aspect since the investigation 

 of the properties of coherent pencils has shown that regular 

 reflection and refraction at the surface of two media is 

 not essentially irreversible. The conclusions at which Dr. 

 Laue arrives are fairly simple and straightforward. If an 

 indefinitely extended train of plane light waves falls on an 

 equally indefinitely extended grating no irreversible change 

 takes place. On the other hand, if the grating is limited 

 in extent the measure of the irreversible changes, in terms 

 of entropy, is equivalent to that produced by difTraction 

 through an aperture equal in size to the grating itself. 

 Thus the larger the area of the grating the less entropy 

 change is associated with the difTraction, and every inter- 

 mediate condition exists between the practically reversible 

 difTraction of a very large pencil of light and the irreversible 

 difTraction of a small one. In the Physikalische Zeitschrift, 

 X., pp. 807-10 (1909), Dr. Laue enunciates analogous con- 

 clusions. He finds that the scattering of light by small 

 transparent particles is irreversible, and that if difTraction 

 at a grating is accompanied by absorption the change of 

 entropy is the same as if the absorption were associated 

 with an equivalent geometrico-optical process. We have 

 here a simple illustration of the futility of formulating a 

 thermodynamical scheme on the dQ/T definition of entropy. 

 NO. 21 10, VOL. 83] 



.At the same time, the principle of coherence does nc 

 render it possible to produce an increase of availabl 

 energy, but only to rescue what would otherwise be lost 

 and this is not inconsistent with a broader enunciation 

 the laws of thermodynamics. 



Messrs. G. Philip and Son, Ltd., have issued a plani 

 sphere of the earth (price 75. 6d. net), devised by Mr. G. F 

 Morell, by which it is possible to determine, with a singl 

 adjustment, the local time corresponding to any givei 

 Greenwich time, or vice versa. The whole surface of ou 

 globe is projected upon a disc about 23 inches in diameter 

 capable of rotation about a point fixed at the North Pole 

 Parts of this disc show through a circular window abou 

 13 inches in diameter on the face of the planisphere, an- 

 around this window the hour lines are marked, so tha 

 the relation between the meridians on the map of the eartl 

 and the time can be seen at once. About three years ag 

 the same publishers produced a " Standard Time-dial," ii 

 which the north and south hemispheres of the earth wer 

 mounted back to back and rotated together on a singl 

 pivot (see Nature, October 31, 1907). The planisphere no\ 

 issued serves the same purpose, and while it has th 

 advantage of enabling the relation between the times a 

 any parts of the world to be seen at a single glance, i 

 sufTers from the disadvantage of great distortion in th 

 case of regions south of the equator. For the consideratioi 

 of relative times this distortion does not matter, though i 

 would be misleading if used for purposes of geographica 

 instruction, and it enables believers in a fiat earth to shov 

 that all the phenomena of local time can be explained 01 

 their theory. The diagrams of constellations inserte( 

 around the circular opening convey a completely wronj 

 impression as to the relation of the stars to the earth 

 but while the planisphere will be of little value education 

 ally, it provides a very convenient means of determininj 

 easily the corresponding standard times at any instant ii 

 different parts of the earth. 



The first edition of Prof. J. Percival's " Agriculture 

 Botany " was published by Messrs. Duckworth and Co 

 ten years ago, and was favourably reviewed in thesi 

 columns (vol. Ixii., p. 570). The work has been accepte( 

 as the standard text-book for agricultural students an( 

 others concerned with practical aspects of botany, and wi 

 are glad to welcome the appearance of the fourth edition 

 A new chapter has been added on the Linacae, with par 

 ticular reference to flax or linseed ; and among the addi 

 tions is an account of Mendelian laws of inheritance, t( 

 which much experimental work has been devoted sinci 

 the original volume appeared in 1900. The book nov 

 contains about twenty more pages than the first edition 

 and the revision and additions will enable it to maintaii 

 the high position it holds among text-books for the study 

 laboratory, and the reference book-shelf. 



A COMPREHENSIVE Catalogue of important works 01 

 mathematics, astronomy, physics, chemistry, and kindre< 

 subjects is comprised in the first part, just issued, of th( 

 supplement to Messrs. H. Sotheran and Co.'s " Bibliothec; 

 Chemico-Mathematica." The notes to many of the work 

 are both interesting and curious, and they make this cata 

 logue a readable publication instead of merely a list o 

 titles of books. 



Messrs. Watts and Co. have issued for the Rationalis 

 Press Association, Ltd., a cheap reprint of Prof. Haeckel': 

 " Last Words on Evolution." The price of the nev 

 edition is sixpence in paper covers and one shilling bouni 

 in cloth. 



