July 17, 19 13] 



NATURE 



505 



Calanus. This would give about 6000 Copepods in the 

 stomach of an average mackerel, or in a live minutes' 

 haul of the tow-net, on this occasion. 



It may be added that these mackerel were evidently 

 not being nourished in accordance with the views of 

 Putter, and were clearly able to fill their stomachs 

 from the plankton around them. 



W. A. Herdman. 



S.y. Runa, Tobermory, N.B., July 12. 



Helium and Neon. 



The experiments communicated to the Chemical 

 Societj recentlj by Prof. Coll ; e and Mr. Patterson, 

 ires delivered by Sir J. J. Thomson, and the 

 discussions which have taken place in Nature, on the 

 possible synthesis of the chemical elements have 

 aroused great interest outside England. So far as 

 I 1 .111 ascertain, opinion is much divided. For my 

 own part I may perhaps be permitted to say that I 

 have always entertained the idea of a possible forma- 

 tion of elements of the helium group from other 

 gases by integration, just as these are formed from 

 other elements by disintegration (see Chemical News, 

 [896, and Berichte, 1899). When I put forward this 

 view objection was taken that 4H is greater than 

 He, 4-032 instead of 3-99, and the same kind of 

 objection may be raised to-day that He + O, or 

 3-94-16, is less than Ne, 20-2 (unless Ne is a mixture 

 of gases). 



In order that the above question might be solved 

 definitely, I would beg to suggest that experiments 

 should be conducted in Rontgen-tubes from the elec- 

 trodes of which every trace of the gases "occluded" 

 or firmly held by them would be first removed by 

 continued bombardment with kathode rays. 



As regards the question put forward by Sir J. J. 

 Thomson, whether the new gas X 3 , discovered by 

 him, may be a new element that fills tie vacant 

 space in VII. group, 1 series (VII-i), in Me ideleeff 's 

 periodic system, I may be allowed to remark that 

 Mendeleeff's prediction of the properties of the 

 elements Sc, Ga, Ge, could be successful, because it 

 was an interpolation ; whereas the prediction of the 

 properties of the element X = 3 includes an extrapola- 

 tion, which is always rather uncertain; besides, the 

 the helium group were unknown at the time 

 of the prediction. Its properties may be derived from 

 the following equations: — (1) Ne:F = He:X; (2) 

 Li:F=H:X; (3) Li:H = F:X; but also (4) 

 Fe:He = Mn:X, and (5) Cu:H = Br:X, showing 

 how uncertain the prediction of its properties be- 

 comes, so that it is indeed probable that it will be 

 more negative than fluorine, but not necessarv that 

 should combine with the silicon of the glass. 



The delicacy of Sir J. J. Thomson's new method 

 has superseded our old methods of investigation in a 

 way similar to that based upon radio-activity, and the 

 results of the study of the new gases discovered by 

 this new method are awaited by chemists with the 

 greatest interest. Bohuslav Brauner. 



Bohemian University, Prague, July 6. 



Red Water and Brine Shrimps. 



By the kindness of Mr. A. W. Sheppard and Prof. 

 A. Dendy, F.R.S., I have been enabled to examine 

 specimens of the brine shrimps from Geelong men- 

 tioned by Mr. Whitteron in his letter (Nature, June 

 12, p. 372). They belong to the species Parartemia 

 zietziana, described by the late Mr. O. A. Sayce in 

 1003 (Proc. Roy. Soc. Victoria, xv. , part ii., p. 232). 

 In Parartemia the unpaired uterine sac is produced 

 into two large dorso-lateral lobes lying on either side 

 of the " tail," and appearing, as Mr. Whitteron says, 

 " like the e,gg sacs of Cyclops." Mr. Savce's speci- 



NO. 228l, VOL. 91] 



mens were obtained from a "brackish-water swamp 

 near Lake Alexandrina, South Australia." It is in- 

 teresting to learn that the species is able also to live 

 in the brine of salt-pans. 



The flagellate described by Mr. Whitteron is prob- 

 ably allied to, and perhaps identical with, Dunaliella 

 salina, which has long been known to cause a red 

 coloration in the brine of salt-pans in Europe and 

 Algeria. A detailed account of this form and refer- 

 ences to the somewhat extensive earlier literature of 

 the subject are given by Clara Hamburger (" Zur 

 Kenntnis der Dunaliella salina," Arch. Protistenk., 

 vi., 1905, p. m). W. T. Calman. 



British Museum (Natural History), 



Cromwell Road, London, S.W., July 12. 



The Maximum Density of Water. 



Physiographers lead us to believe that the earth 

 is defended from a profound glaciation, cumulative 

 from year to year, by the law that water is heaviest 

 at a temperature of four degrees above centigrade 

 zero. If the main cause lies here, it is desirable that 

 this measure should have its peculiar power set forth 

 with more precision than has been customary. 



The matter usually presents itself to students rather 

 differently. The predominant fact is the floating 

 power of ice. Hereby the water is screened from 

 further attacks of the cold air, and dispersal is provided 

 in the puzzling conditions of ground or anchor ice. 

 Next perhaps in importance is the slow conduction 

 of cold bv water. Then comes the large value of the 

 latent heat of water. It is not obvious why there 

 should be disastrous results if the maximum density 

 of water were at o° C. The four units may be 

 viewed as a helpful margin of safety rather than as 

 an essential ; but they would appear to be neglig- 

 ible in comparison with the 79 units of latent heat. 

 Water at o° C. is by no means unstable ; each gram 

 weight as it passes into ice throws out amongst its 

 neighbours an amount of heat which is an effective 

 safeguard against sudden and extensive solidifying. 



W. B. Croft. 



The College, Winchester, July 5. 



Radio-activity and the Age of the Earth. 



1 v\[ gratified to learn from Dr. Fermor's letter in 

 Nature for July 10 that there is a scientific possibility 

 of conceiving how the interior of the earth may be 

 devoid of radio-activity. But if " high pressure and 

 temperature " can inhibit the dissociation of " poten- 

 tially radio-active" substances, will they not do so 

 also in the interior of the stars? If so, radio-activity 

 will no longer be available to prolong their radiation 

 of energv, and we shall be back in the old difficulty 

 about the age of the sun. Indeed, it will be aggra- 

 vated, because we now have positive evidence for a 

 high antiquity of the earth, while still unable to 

 explain that of the sun. F. C. S. Schiller. 



Corpus Christi College, Oxford, July 11. 



THE GENERAL MAGNETIC FIELD OF THE 



SUN. 1 

 'FHOSE who are familiar with Prof. Hale's 

 brilliant discovery of magnetic fields in sun- 

 spots, and are aware of the difficulties con- 

 nected with that investigation, will greatly admire 

 his courage in seeking to establish the much 

 weaker general magnetic field of the sun itself. 

 The following condensed account of the method 

 adopted and results obtained is given, to some 



* Based upon an advance proof of a paper by Prof. G. E. Hale which is 

 [ to appear in TJic Astrofihysical Journal. 



