I 



June 29, 19 16] 



NATURE 



3^ 



account of this bridge appears in Engineering for June 

 23. The bridge was designed by Mr. T. B. Ball, the 

 engineer of the railway company, and provides for a 

 double line of railway and for a broad road bridge, 

 with footpaths parallel to the railway track. The lift- 

 ing span gives a clear waterway 150 ft. in width. 

 The operating gear is provided with two electric 

 motors, each of 115 horse-power, and these are con- 

 nected by gearing to the main gudgeon pins at the 

 outer girders. The bridge is accurately balanced, with 

 a slight preponderance to the nose end in order to 

 prevent hammering on the bearings. The gear is 

 sufficiently powerful to operate the bridge against a 

 20-lb. wind, and the time for opening, or closing, is 

 three minutes. The bridge was constructed by Sir 

 William Arrol and Co., Ltd., of Glasgow. 



OUR ASTRONOMICAL COLUMN. 



Comet 19156 (Taylor). — Messrs. Jeffers and Neu- 

 bauer, of the Berkeley Astronomical Department (Uni- 

 versity of California), have calculated elements and 

 ephemeris for this comet. Three normal places were 

 formed from the observations, 1915, December 5-10; 

 1916, Januar}- 7-1 1 and April 5, the latter being photo- 

 graphic (Lick Obser\^ator)- Bulletin, No. 281). The 

 new orbit agrees ver\- closely with the Copenhagen 

 calculation (Nature, March 16; see also issue for 

 February 17) : — 



T = l9i6 Jan. 30-9403 G.M.T. P— 6-3662 years 

 M = S57-345o'' 



Epoch 1916 Jan. 3'5 ti-M.T. 



Equinox i9i6'o 



• =354' 49' o''6" 

 = 113' 54' 05-1" 

 / = 15° 31' 435" 



^Io = 356' 31' 330" 



e =0-546458 (<^ = 33^ 7' 277") 

 Log <j = 0535922 



The ephemeris has been calculated to August, but 

 the comet is stated to have been only of the fifteenth 

 magnitude early in May. 



Return of Daniel's Comet (1909^). — According to 

 new elements calculated by S. Einarsson and Margaret 

 Harwood, the undisturbed time of perihelion passage 

 is 1916, May 23-422 G.M.T., but the ephemeris shows 

 that the comet will not be favourably situated for 

 observation. 



• Variation of Latitude. — In the course of a review 

 of this subject Prof. F. Schlesinger incidentally men- 

 tions that on account of the war the second American 

 station of the International Latitude Service may pos- 

 sibly be closed down (Proc. American Philosophical 

 Societ}-, vol. liv.. No. 220). The two American stations 

 ?\-ere Gaithersburg and Ukiah. The former has 

 already been abandoned (N.ature, March 2). An 

 American observ-atory — Cincinnati — participates, but, 

 of course, is not maintained bv the international 

 organisation. 



Difference of Longitude between Paris and 

 Washington. — Prof. Abraham's photographic method 

 of recording wireless time signals has been tested 

 during the past winter in the determination of the 

 above long arc. For various reasons only seven pairs 

 of records are available for reduction ; nevertheless, 

 cximparison with the results obtained bv telephonic 

 reception is- decisively favourable. M. Baillaud 

 {Cotuptes rendus, No. 24) states that the Bureau of 

 Longitudes has come to the conclusion that for the 

 determination of longitudes over distances too great 

 for the transmission of verA' short signals the only 

 method which can be employed with success is that 

 of photographic registration. 



The CoNSTrTLTiON of the Milky Way. — Prof. C. V. 

 Charlier has published a preliminary statement of 

 results obtained at Lund on the distribution of the 



NO. 2435, VOL. 97] 



helium stars. The special significance of this group 

 of celestial bodies is due to their close and real asso- 

 ciation with the Milky Way. As it now appears that 

 the whole class (804 stars) has been catalogued at 

 Harvard, they afford a unique body of data for statis- 

 tical investigation (Cotuptes rendus, No. 23). The 

 luminous radiation of these the brightest and hottest of 

 stars is such that, viewed at the limits of the stellar 

 universe, one of them would still appear as an 8th 

 magnitude star. The nearest of the type is 4 sirio- 

 meters (1 S.M. = 1,000,000 astronomical units) distant, 

 and the most distant 250 S.M. The centre of the 

 group — considered to be the probable centre of the 

 sidereal universe — is situated in the direction of 

 Carina (o=7-7h., S= — 55-6°). Two-thirds are contained 

 in an ellipsoid of revolution having axes of 37-3 and 

 13-1 S.M. in the plane of the galaxy and at right 

 angles respectively. 



HYDROLOGY AT THE ARCTIC CIRCLED 



THERE is something mysteriously fascinating about 

 regions which are remote from the ordinary- 

 haunts of men. The silence of illimitable wilds and 

 the solitudes of eternal snow stir the heart and stimu- 

 late the imagination as no other field of human enter- 

 prise can do. Explorers feel the irresistible call ; 

 pioneers grope their lonely way; by degrees the track- 

 less unknown is traced and probed and scanned, until 

 the survey is complete and earth's secret recesses 

 are defined as completely and accurately as an English 

 coimty. 



Such is the reflection which arises as one turns over 

 the pages of the extremely interesting hydrographical 

 record of the Yukon-Tanana region, Alaska. Lying 

 along the Arctic Circle, hemmed in by frozen seas and 

 peaks of ice, this great tract of 40,000 square miles 

 has been patiently mapped out aiid indexed throug^h 

 six long years, with praiseworthy persistence and 

 energy, by workers in the United States Geological 

 Survey. The preface does them but bare justice when 

 it points out that their investigations have necessitated 

 journeys which have put their physical endurance to 

 severe tests and entailed considerable hardship. 



The Yukon-Tanana region forms part of the central 

 plateau of Alaska. It is an upland diversified by many 

 broad valleys, with fiat, interstream areas, above 

 which rise numerous rounded domes and mountain 

 masses. The surface of the upland ranges from 2000 

 to 3500 ft. in altitude; the domes, irregularly distri- 

 buted, reach 4000 to 5000 ft, and the highest moun- 

 tain crests to 6000 ft. high. The domes are almost 

 entirely composed of igneous rocks, and the mountains 

 of these and closely folded sediments, .-^s a geological 

 field, the country' is one of great interest ; it is a region 

 of sedimentation, diastrophism, widespread meta- 

 morphism, abundant intrusion, and volcanic action. 



The rocks may be divided into two principal groups : • 

 one consisting of metamorphic schists of pre-Ordo- 

 vician origin, and the other, ranging in age from 

 Ordovician to Carboniferous, made up of folded argil- 

 lites, quartzite, conglomerate, sandstone, and lime- 

 ^tone, resting unconformably in relation to the schists, 

 larneous rocks are represented by areas of granite and 

 by dykes of varied composition. The most notable 

 : uneral resource of the country is placer gold, the 

 developed deposits of which lie chiefly among the elder 

 schistose and intrusive rocks. Silver, antimony, 

 silver-lead, and tin ores are also worked. 



As might be expected, the climate is one of estrones. 



l'"Snrf«ce Water Supolr of tb« YBkoa-Tanma Region. Alaska." By 

 C. K. Eltsworth and R. W. Davenport. (Water Supp'v Paper No. 342.) 

 ^'P- 34'>> with *>»p*, photographs, and diagraois. (Washingtoo : Unaed 

 -^:ates Geological Surrey. 19T5.) 



