NATURE 



[May 9, 1895 



If, as is the cas4.^ in practice, the alternations are fairly rapid, the 

 appearance presented is that during the |iassage of the current 

 the two halves of the field ap|>ear equally bright when the 

 analyser is adjusted in the zero position for no current |>assing. 

 By adopting the stroboscopic method of observation, the author 

 has, however, succeeded in making clear the different phases of 

 illumination through w hich the field of view |iasses. By suitably 

 adjusting the difference (t) between the period (T') of the strobo- 

 scope and the |K-rio<l (T) of the current, it is possible to see the 

 \'arious phases of the phenomenon pass as slowly as is desirable, 

 the period of the ap|iarent change being to the period of the 

 current in the ratio of T' to «. Hence, by determining the time 

 taken to go through a whole cycle of the apparent changes, the 

 |xrriod of the current can Ix; deduced. The maximun> value of 

 the current can also be detennined. If we denote by fj. the 

 rotation of the plane of |Xilarisation of the light corresiwnding 

 to the maximum current, then, when the principal plane of the 

 anal)°scr is rolale<l through a less angle than /i, the two 

 halves of the field w ill ap|>ear equally bright twice during each 

 cycle of the ap|>arent changes. If the angle of rotation of the 

 analj'ser is /», thus equality will only occur once in a cycle, while 

 if the rotation is greater than ^, at no time will the two halves of 

 the field of view ap|>ear equally bright. Thus it is quite easy to 

 •Ictermine the |>osition of the analyser corresponding to the 

 maximum current. The method also admits of obtaining the 

 current curve, by noting the times at which, when the angle of 

 rotation of the analyser (o) is le.ss than /i, the two halves of the 

 field are equally bright. The current corresponding to the two 

 times observed can Ije calculated from the \-alue if o, the known 

 dimensions of the coil, and Verdet's constant for the liquid 

 employed. 



I'ROF. Kkank Clowes' " Treatise on Practical Chemistry and 

 Oualitative .\nalysis," adapted for use in the laboratories of 

 colleges and schools, has reached a sixth edition. Messrs. J. 

 and A. Churchill are the publishers of the book. 



"^uv. Quarterly /oz/rna/ of the Geological Society, just is.sued 

 ■(No. 202), contains, in addition to jwpers read at the meetings, 

 the report of the proceedings of the annual meeting and the 

 anniversary address of the president. Dr. Henry Woodward, on 

 "Some I'oinLs in the Life-history of the Crustacea in Early 

 I'alaxizoic Times." 



TlIK very useful jiamphlet entitled "Notes on I'olarised 

 Light," by Mr. \. K. Munby, which we favourably noticed when 

 it ap|)e.-ire<l alHiut a year ago, has been translated into Ru.ssian 

 by I'rof. Clinka, of .Si. Petersburg University. Students of 

 mineralogy lieginning wurk with the ]>olari.scope, will find the 

 contents of the (lamphlel of great assistance. 



\Vb have received a rejKirt of the proceedings of the con- 

 ference on inland navigation, held in Birmingham in Kebruary, 

 by the Federated Institution of Mining Kngineers. The re|)ort 

 <:ontains .some useful information on the im|iorlanl subject of the 

 inland navigation of (Jreat Britain, and a numlxjr of valuable 

 .suggestions for im|iroving the present ineflicieni state of our 

 inland waterways. 



MK.SSRS. Diii.Af ANii Co. have pre|Kire<l and published a 

 useful catalogue of se|«rate |>a|>ers from the Philosophi<iil Trans- 

 attiom of the Koyal Society riffered for sale by them. The 

 |ia|x;rs are indexed according lo the authors' names. Two other 

 new catalogues which scientific bibliographers will find valuable 

 arc k. h'ricdlander and Son's " Biicher-verzeichniss " (No. 417). 

 containing titles of entomological works, and a list of lxx>ks 

 Luucd by Mr. Bernard (Juaritch, Piccadilly, S.W. 



Scicnte Gossip for May contains several articles oi scientific 

 interest. Dr. Dallinger has a note on Meliterla riiixciis, illus- 

 >rale<l by drawings of this small (hough interesting denizen of 



NO. 13.^2, VOL. 52] 



our ]x)nds. Messrs. Wanklyn and Coo|)er write on Argon. Mr. 

 Thomas Leighton h.is an article on "C.eology of the Isle of 

 Wight": and Dr. Guppy writes on "Stations of Plants and 

 Buoyancy of Seeds." Mr. Rudolph Beer has an interesting 

 illustrated article on " Leguminous Plants." 



Thk West .\ustralian \' ear-Book for 1S93-94, issued by the 

 Kegistrar-t'.eneral, contains tables showing the results of meteoro- 

 logical observations at the chief obser\iiig stations, together with 

 .some general remarks on the climate of the colony. The climale 

 varies a good deal i[i the different jjarts ; in the south and south- 

 west it is excelleiit, being temperate and cool, with regular ami 

 sufficient rainfall. To the eastward the climate is'lrycr, but little 

 accurate information is available in that direction. 



The Re|X)rt of the Royal Zoological Society of Ireland for the 

 year 1894, shows that the Society is in an exceedingly prosperous 

 condition. Nine lion cubs were born during the year, fo\'r ol 

 which died, but the five others (all males) were disposed of as 

 exchanges. There are still two lions and five lionesses in the 

 gardens of the Society. The Council has tlccided to make a 

 donation to the funds of the Irish .\'aliiraiist,a. monthly journal 

 which frequently contains valuable information on the natural 

 history of Ireland. 



Wk have received No. 2 of the {Jfticial Guide lo the Museums 

 of Kcononiic Botany at the Royal tiardens, Kew, compris- 

 ing Monocotyledons and Cryptogams. Among the speci- 

 mens and products belonging to Monocotyledons, by far the 

 larger number are naturally derived from the great order of 

 palms ; though the origin is also illustrated of other very im- 

 portant jiroducts, .such as vanilla, ginger, grains of |->aradise, 

 arrowroot, the pine-apple, aloes, bananas, the yam. New Zealand 

 hemp, dragon's-blood, and many others. The jialms include 

 nearly too distinct exhibits, and the grasses upwards of 60. 

 .Among Cryptogams, .several officinal and other useful articles 

 are obtained from the fibres ; while the -Mgx and I'ungi also yield 

 their quota. .\ very copious index adds greatly to the value of 

 this publication. 



A KEI'OKr, lately issued, on the progress anil develojmient of 

 the Manchester .Museum, Owens College, during the past four 

 years, .shows that the museum is a great jiower for good. By 

 means of short courses of popular lectures, and informal demon- 

 strations and addres.ses, the collections have been rendered more 

 interesting and intelligible to the public. Clubs, societies, and 

 classes have jiaid frequent visits of inspection, and have had the 

 contents of various sections of the museum explained to them by 

 Prof. Boyd Dawkins, or by members of the museum staff. .\ 

 number of additions have been made in the geological depart- 

 ment, one of the most interesting accessions being a model of a 

 gl.acier, made to .scale by I'rof. lleim. The zoological and Ixitanical 

 collections have also been l>enefited by ailditions, and the .speci- 

 mens in most of the sections have been reduced to law and 

 order. 



A RECENT redetermination of the atomic weight of slroiilium, 

 by T. W. Richards, confirms the value S770 foun<l by Pelouze 

 in 1845. Pelouze employed the methoil founded on a comparison 

 of anhydrous .strontium chloride and silver. The ]>resent author 

 finds (I) the ratio between very carefully purified anhydrous 

 .strontium bromiile and .silver in three sets of analy.ses carried 

 out by different metlxHls, and (2) the ratio 2AgBr : SrBr.^ in 

 two other .series of ex|>eriments. Taking oxygen = l6'000, 

 the values obtained for the atomic weight of slriuiliuni are 

 res|)cclively (I) 87-644; 87663; 87-668, and (2) 87-660; 

 87-659. The mean value from these results may be taken as 

 8766. 



The additions to the Zoological Society's tiardens during the 

 past week include a Conmion Stpiirrel {S<ii4riis vulgaris), 



