2l6 



NATURE 



[November 14, 1918 



* =+43° 3i'±o-2S° 

 a =i45-6g±o-38 

 ^,=4271 ±0-33 



1 entre oJ mass describes an elliptic orbit in a 



id .'i 54-08 days, with a semi-amplitude ol 33 km. 



pei second. The spectral lines varj in width, and 



broadest near periastron. Some ol the peculiar!-, 



ties "f the stai ma} be due to its being actually in- 

 volved in the nebulous matter In which 

 ndi d. 



A Rem m;k vbi i Helium v ir. \ notabli 1 1 



tion to the Mile- that the helium stars are usually 

 characterised l>\ small parallax, small proper m 

 .ind low radial velocit; has been found b) Mr. J. 

 Voute in the star Boss P.G.C. 1517 (Astrophysicai 

 Journal, vol. \lviii., p. 14.)). The investigation was 

 undertaken at thi uj i n ol Prof. Kapteyn, who 

 had suspected thai this tai might be found to have 

 the unusuall) large parallax ol about .1 tenth of a 

 second. Mr. VoOte's result is + 0-069" ±o-oo6", in 

 good agreement with Prof. Kapteyn 's supposition. 

 For the propei motion Mr. Voute has found 

 +0-235" =0-01853., but this is greatly in excess "I the 

 value o-ooois. given in Boss's catalogue, and needs 

 further confirmation. The radial velocity of the star 

 is al 1 amounting to I 83 1cm. 



cond. The position of the star for [900 is 

 R. \. tih. om. 57s., decl. — 32 10' 12", and the magni- 

 tude 5-6. 



The Orbii of Sikhs. The results of a imw deter- 

 mination of the elements of the orbil of Sirius arc 

 'i by Dr. R. Vitken in Lick Observatory Bulletin, 

 No. 316. The elements with their probable errors 

 are : — 



P = 5o'o4 years ±o'on yeai 



T= i894"i33±o'oi 1 year 



<• =0594; ±0-0023 



a =7-570" 



Dr. Aitken concludes that the available micrometric 

 and spectrographic data give no evidence of depar- 

 ture from undisturbed elliptic motion. It will be 

 observed that the period given above is in close agree- 

 ment with that nl ;oo2 -ears recently deduced b) 

 Jonckheere. 



PRODUCTION IN THE SEA. 1 



A HIGHLY interesting report by Dr. C. G. J. 

 ■**■ Petersen describes the methods and results of 

 1 work on the evaluation of the bottom fauna 

 and flora of the sea in the Kattegat, Limfjord, ami 

 elsewhere. Abandoning the use of the dredge, as 

 affording misleading ideas of the abundance of life 

 on the bottom, the author invented his "bottom- 

 piers," which are apparatus thai can lift up a 

 ill nf the sea-floor with its contained animals and 

 plains. The area of bottom lifted varies between 

 ii- 1 and 1 square metre, the smaller apparatus being 

 used .u the greater depths! B) a process of washing, 

 the organisms are removed, counted, and weighed. 

 The plates represent typical results, all the organisms 

 found being drawn, in actual size, on paper j square 

 metre in area, which is then reduced to § in. line. a. 



Very often thi bottom deposit consists of a "black, 

 malodorous mass ol sulphurous mud," and it was 

 difficult to it animals could utilise this as 



fund. Sampling ns of a glass tube thrust 



down into it, it was, ho ever, -ecu that there was a 

 thin surface layi quil different composition, 



grey or brown in 1 ■ ;ed .■■ il h 1 egetable 



remains. Oysters ai 1 other bivalves and demersal 



us do not feed mi the black mud or on 

 plankton in the water, bul " literall; stuff themselves 



1 Report of the Danish Biolocica! Station to the Danish Board of Agri- 

 : 1 Bottotl i. tion of Fish Food." By C. G. 



Joh. Petersen. Pp. 62 + 10 plates + ch;,rt. (Copenhag. 



-559, vol. 102] 



with this upper layer of line detritus." "Thi 

 bulk ol the bottom mu ieo ssaril) 



be, herbivorous." Thej mostl) burrow- in the mud, 

 but a large number an attached to solid objects, 

 and shells. These constitute the bottom epi- 



The bottom fauna in general may be divided tiff 

 into ■■ communities, •• eai Ii 1 ii 

 moi 1 pn dominant Forms ; thus the author desi 

 the bottom in the deeper parts of the Katteg; 

 inhabited by communities of Amphilepis pecten, 

 B, chiajei, and Echinocordalurv tili- 

 formis, the typical forms present in each cast 

 indicated b tl ematic names. 



Thi urvi being tntitativi on< , an att 



n actual estimate of the mass of life in the 

 whole Kattegat. There are about 24,000,01 



Zostei 1, 50,000 'oils of plain, I Q ions ,,l 



701 ns of herrings, 25, tons of starfishes, 



50,000 tons nl predator) Crustacea adi] i 



ro,i ions of small fishes, with, of course, much else. 



These estimates are based, not only on the results of 

 bottom-samples, bul also on fishery statistics, the very 

 probable assumption being made that the fish 

 i- practically constant, so that the fraction taken in 

 commercial fishing represents the production. 



No attempt is made density of life on 



sea-lie 1 Ii. in and land. " Strangi . il ma\ seem," sa - 



the author, "there does not exist an) sut 



! 1 immunities on land based upon quantit; 

 investigations ol the commonei species." |. |. 



MILITARY EXPLOSIVES OF TO-DAY A 

 HERE have been no epoch-making discoveries in 

 1 1 as, sa) . the discovt r\ of nitro- 

 glycerine for man) years. Nitroglycerine, disco 

 in 1846, still remains the most powerful explosi 

 practical use Many useful advances have been and 

 are being made, bul it. new 



mixtures of old materials, given fane, names. The 

 nations at war use practically the 1 ives, 



and no one can be said to be ahead of the oth rs. 



The following table gives a comparison of somi 

 the most typical explosives in use: — 



.„*- (13 percent. Nitrogen) 923 03 



Cordit. Mk. I (N!g. - 57, N.< 



Vaseline=0 



Cordite M.D. (N.G. = jo, '. 

 Vaseline=s) 



Ballistic (N.G.=5o, NX. 



bili<er = o- 5 ) 



'Fieri. Acid (Lyddite) 



I he coefficients correspond fairly well with the 

 results obtained in practical use. 



Detonating substances are called higl 

 and their immense sli.it t> ring effect is due, not only 

 to the volume of gas and quantity of heal, but also 

 to the velocity of detonation and density of the ex-, 

 plosive. Shattering power is proportional to 



Volume of gas pi I per gram x velocity 



isity. 



' From three Cantor Lectures delivered before the Royal Society of Arts 

 n April la-t by .1. Young, Chief n Science, Royal Military 



v, Woolwich. 



