June 21, 191 7] 



NATURE 



ZZ^ 



broken for exact determination, and Dr. Eastman has 

 not attempted any new study of them ; but he describes 

 a small dermal plate of Astraspis, which he compares 

 with the median dorsal shield of the European 

 Devonian Psammosteus. Among- Lower Carboni- 

 ferous remains from Missouri he identifies an interest- 

 ing new form of the supposed Chimaeroid head-spine, 

 Harpacanthus. Triassic fishes are well represented 

 in the collection, and parts of the trunk apparently of 

 a new species of Lepidotus are described from Utah. 

 The Jurassic and Cretaceous fishes are scarcely noticed, 

 but there are several brief descriptions of American 

 Tertiary fishes illustrated by well-reproduced photo- 

 graphs. 



A COMMUNICATION has reached us from Messrs. Bell- 

 ingham and Stanley, Ltd., in which attention is 

 directed to an interesting point in connection with the 

 design of the Zeiss Abbe refractometer. It has been 

 observed recently by users of the instrument that, 

 owing to want of illumination, measurements cannot 

 be made for liquids having a refractive index greater 

 than 1-52. It is plainly stated in the Zeiss catalogue 

 that the Abbe refractometer may be used for the 

 measurement of refractive indices from 1-30 to 17, 

 and that the liquid to be examined is enclosed between 

 two prisms of flint glass. In the instrument as actually 

 constructed it appears that a crown glass prism of. low 

 refractive index (Nn=i-52) has been substituted for 

 the dense flint prism (Nd=i-75) used at first as the 

 lower or illuminatinp- prism. The contact surface of 

 this prism is left unpolished, so as to scatter the light 

 entering the liquid film. The process of wiping the 

 surface to remove the liquid which has been examined 

 results in the removal of the thin sharp w-alls left by 

 the abrasive, and the surface approximates to a 

 polished face. When this is the case very little light 

 can fall on the contact surface of the liquid and the 

 upper prism at angles greater than the critical angle 

 unless the lower prism has a refractive index greater 

 than that of the liquid under test; for it is only when 

 this condition is satisfied that light entering the liquid 

 is bent away from the normal. Several such instru- 

 ments have been rendered serviceable for the measure- 

 ment of liquids of refractive index as high as 1-70 by 

 replacing the crown illuminating prism by a suitable 

 dense flint prism In using the refractometer for 

 solid and plastic bodies it would be more convenient 

 if the prism box were designed to open away from the 

 operator. 



Engineering for June 8 contains an illustrated 

 account of the reconstruction of the Union Pacific rail- 

 road bridge at Omaha. The new bridge consists of 

 four through Pratt-riveted chord spans, 246 ft. long, 

 one through riveted span 130 ft. long, and two through 

 Pratt-riveted spans 120 ft. long, four deck-plate girders 

 67 ft. long, and two deck-plate girders 50 ft. long, for 

 two tracks. The total length of the bridge is 1722 ft., 

 excluding approaches; the total weight of the new 

 bridge is about 11,250,000 lb., as against 5,500,000 lb. 

 in the_ old bridge replaced. The new bridge rests on 

 the original piers, and, in order to interfere with traffic 

 as little as possible, the following method of recon- 

 struction w^as adopted. The original piers were ex- 

 tended on the up- and down-stream sides by temporary 

 timber piers. The new spans were erected complete on 

 the temporary down-stream piers. The bridge was 

 closed for traffic shortly after 11 a.m. on December 23, 

 1916, and by twelve o'clock the old spans had been 

 rolled on to the temporary up-stream piers. The new- 

 spans were then rolled into position on the piers, this 

 work being completed by 4 p.m. Track crews then 

 closed up the track?, and signalmen bonded the joints 



NO. 2486, VOL. 99] 



so that automatic signals were restored to operation, 

 immediately. Traffic over the bridge was restored at 

 9.39 p.m. The design and construction of the new 

 bridge have been handled under the direction of Mr. 

 E. E. Adams, consulting engineer of the Union Pacific 

 system. 



The valuable scientific work carried out by Austra- 

 lian men of science is conspicuously shown in the 

 thirty-ninth volume of the Transactions of the Royal 

 Society of South Australia (1915). More than 800 

 pages, illustrated by seventy plates, are occupied by 

 papers in various departments of science. Most of the 

 shorter papers deal with zoology or botany, but geology 

 and astronomy are also represented. Among the 

 longer papers are notes on the " Fishes of the South 

 j Australian Government Trawling Cruise, 1914," by 

 E. R. Waite and A. R. McCulIoch ; an account of the 

 "Natives of Mailu, Papua," by Dr. B. Malinow-ski; 

 and " Scientific I^otes on an Expedition into the North- 

 western Regions of South Australia," by members of 

 the expedition. The report of the society also records 

 its activities in the popularising of scientific studies by 

 lectures, exhibitions, and excursions, in the discovery 

 of new animals and plants, and in the preservation of 

 Australian fauna and flora. The committee and mem- 

 bers of the society may be congratulated on their fine 

 record. 



A TREATISE on " Gyrostatics and Rotational Motion " 

 by Prof. Andrew Gray is in the press, and will be 

 published by Messrs. Macmillan and Cch, Ltd., as 

 soon as present circumstances permit. The work aims 

 at giving a complete account of tops and gyrostats, 

 gyrostatic action in machinery, and gyrostatic appli- 

 ances. The general theory is fully dealt with, but an 

 attempt has also been made to treat all the more 

 important special problems by direct reference to first 

 principles in each case. Mathematical difficulties are 

 not avoided, but the relative importance of physical 

 Ideas has been kept in view and enforced by careful 

 descriptions of the latest practical gyrostatic inven- 

 tions, so far as the public service permits. 



Messrs. O. Doin et Fils, of Paris, have begun the 

 publication of a series of handy volumes entitled " Bib- 

 lioth^que de Biologie G^n^rale," under the editorship 

 of Prof. M. CauUerv. Up. to the present two works 

 have been issued, but volumes have been arranged for 

 dealing respectively with Les Phenomenes vitaux; La 

 Cellule (Morphologic et Physiologie), Prof. M. Henne- 

 guy ; Les Formes larvaires et les Metamorphoses, 

 Prof. C. Perez; La Reproduction asexuee; La Re- 

 generation et la Greffe, E. Bordage; La Sexuallte et la 

 Parthenogenese , Les Correlations organiques et ITn- 

 divlduallte, E. Guyenot; LTrritabilite et les Tropismes ; 

 Les Mutations materielles dans les etres vivants 

 (aliment et milieux nutritifs) ; Les Mutations energlques 

 dans les gtres vivants (lumlnoslte, chaleur, electricite, 

 etc.) ; La Biologie des Pigments, Prof. J. Cotte ; 



[ Ethnologie et Organisation ; Commensalisme, Sym. 



I biose. Parasitisme ; Les Milieux biologlques marins, 

 P. M. de Beauchamp; La Biologie des eaux douces; 

 Les princlpaux facias biologlques terrestres ; La Con- 

 currence vitale ; L'Heredite; La Variation; L'Hybrida. 

 tion ; L'Esp^ce ; L'Adaptation ; La Phylogenie ; and 

 Les Theories evolutionnistes. 



The Rede lecture, on " Science and Industry : the 

 Place of Cambridge in any Scheme for their Combina- 

 tion," which was delivered on June q by Sir R. T. 

 Glazebrook, and is abridged elsewhere in this issue, is 

 to be published immediately by the Cambridge Unlver- 

 sltv Press. 



