42 



NATURE 



[November 9, 191 1 



Kpoch November 17, 3h. 3oni., tenth order of magnitude. 

 I'rincipal maximum, Novemb. 1 17. i7h. 25m.; secondary 

 maxima, November 17, 23h. :<..iu., and November 18, 



sh. sm. , , . , 



' Epoch November 17, ish. 30m., approximately sixth 

 (Mil. I (il magnitude. Principal maximum, November to, 

 \A\. 55m.; secondary maxima, November iS, 1511. 15111., 

 and November 19, ash. jom. 



Kpoch November 24, 2h. 30m., approximately fourth 

 <.i(ler of magnitude. Principal maximum, November 23, 

 5I1. :;(iiii. ; secondary maxima, November 2j. 1511 20m. 

 ami iSli. 20m. 



Epoch November 25, 4h. 40m., eighteenth order of 

 magnitude. Principal maximum, November 24, 2h. 3Sm. ; 

 srcondai V ninximn, November 24, i2h. 40in. and 23h. lom. 



Ii i^ sioiiitirant that, of the eight principal epochs of the 

 iiu.nlli. 110 fewer than six fall due during the period of 

 Ndv.'inlxr 9-20. This, therefore, is the part of the month 

 richest in meteoric events. The two remaining epochs of 

 .November 24-25, though nominally strong, do not rank in 

 importance with the foregoing six. 



Of these six there are three that call for special men- 

 tion. The first, commencing on November 9, has the 

 highest meteoric intensity of the month ; but the epoch of 

 November 17, 3h. 30m., may prove to be the most interest- 

 ing, as it bears a certain resemblance to the epoch of 

 November 15, 1905, and in the writer's opinion is liable 

 to be associated with auroral phenomena. The small inter- 

 mediate epoch of November 13, i6h., is the only one that 

 places maxima between i2h. and i8h. on any of the three 

 nights November 14-16, two of its secondary maxima 

 becoming due between these hours on the night of 

 November 16. The general Leonid maximum will there- 

 fore probably be best observed on the night of 

 November 16,' but late members of this well-known star 

 shower are likely to be strongly in evidence also on the 

 following night. John R. Henry. 



2 Belgrave Villas, Rathmines, Dublin, November 6. 



Tick (Ixodoidea) Generic Names to be included in the 

 " Oflfical List of Zoological Names." 

 (i) The international committee invited by the secretary 

 of the International Commission on Zoological Nomen- 

 clature to make a detailed study of the nomenclature of 

 ticks (Ixodoidea), and consisting of the following specialists 

 in this group, W. Donitz (Berlin), Albert Hassall (Wash- 

 ington), L. G. Neumann (Toulouse), G. H. F. Nuttall 

 (Cambridge), and Cecil Warburton (London), has submitted 

 its first report. 



(2) Said committee unanimously agrees that the follow- 

 ing eight generic names are the correct names for the 

 genera in question, and that the correct genotypes, accord- 

 ing to the international rules of zoological nomenclature, 

 are the species cited : — 



Amhlyomma Koch, 1844a, 223-231, type cajennense 

 Fabricius, 1787. 



Argas Latreille, 1796a, 178, type reflextts Fabricius, 

 1794. 



Dermacentor Koch, 1844a, 235-237, type rcttculattis 

 Fabricius, 1794. 



Haemaphysalis Koch, 1844a, 237, type concinna Koch. 

 Hyalomma Koch, 1844a, 220-223, type aegyptititu 

 Linnaeus. 



Ixodes Latreille, 1796a, 179, type ricinus Linnaeus. 

 Rhipicentor Nuttall and Warburton, 1908, 398, type 

 bicornis Nuttall and Warburton. 



Rhipicephalus Koch, 1844a, 238, 239, type sam^uint'iis 

 Latreille. 



(3) Notice is hereby given that the undersigned will wait 

 until May 1, 1912, for any zoologist to raise any objection 

 to any part of the report of the special committee. If no 

 valid point is raised by the date mentioned, the under- 

 signed will transmit the list to the International Com- 

 mission with the motion that these names be incorporated 

 in the " Official List of Zoological Names " provided for 

 by the last International Zoological Congress. 



All correspondence on this subject should be directed to 



C. W. Stiles. 

 (Secretary International Commission 

 on Zoological Nomenclature.^ 

 Hygienic Laboratory, Washington, D.C., October 30. 



NO. 2193, VOL. 88] 



Localising Minute Le«k» in Vacuum Apparatus 



In view ol the fact that in many 

 research there has arisen of late y 



complicated apparaliis tO be kept 



exliau^liMii 

 siin|>l'' iii'tli 

 In th. r:> 

 for iiian\ 

 inelho.l. 'll 

 from the apparai 



A physii. 

 'cessily fi 

 1 1 ; gh state 01 

 to hear of a 



t 1. ;,k 



Uerest your reader 



alising minute leaks. 



ks in '* all glass " apparatus, I havei 

 ith success Goldstein's sparkJ 

 disconnecting the kathode leadl 



uu.M ..... .H, . i >g in a small alternate spark- 1 



gap, and exploring over the suspected joints with the loose s 

 lead until a brilliant discharge to the 'nside of thel 

 apparatus indicates the position of the leak. The objer 

 tions to this method are that if parts of the glass a: 

 very thin a hole may be made where none previous!, 

 existed; it obviously cannot be used near a terminal, or 

 at all with a " wax " joint. .... ^ 



An apparatus of mine involving seven distinct and 

 complex sealing-wax joints recently developed a micro- 

 scopic leak of about i/ioo mm. per hour. Being fac* 

 with the alternative of pulling the whole apparatus dov 

 and remaking every joint, it occurred to me that t- 

 extremely sensitive nature of the discharge in air to chan: 

 its colour when in the presence of carbon compounds 1 

 is, in fact, by the change from the grey of CO to t; 

 crimson of N that leaks are generally first seen) mig;. 

 be used with advantage. I therefore wiped each joint 

 over with a small pad of cotton-wool soaked in petrol, 

 keeping the discharge going meanwhile, and the instant 

 the real offender was reached— a " metal-wax-glass joint 

 in this case— the discharge turned abruptly from red to 

 blue. The method seems extraordinarily delicate, and 

 should be applicable to all cases of air leak so long as 

 the latter is not so large as to prevent the discharge 



P^'"'"^- F. W. .\STOS. 



Cavendish I.alx.ratory, Cambridge, October 31. 



Multiple Rainbows. 



On Tuesday morning last, October 31, a succession of 

 rainbows of extraordinarv brilliance was visible here. The 

 most brilliant appeared at 8.45 a.m., and lasted about five 

 minutes. . . , ^ 



The sun was shining brilliantly, and the atmosphere to 



the east was remarkably clear, while the rain-storms came 



up from the Bristol Channel, eight miles to the west. At 



8.45 a.m. six rainbows were visible, three inside the mam 



bow and verv close to it, the colours being in the same 



order as those on the main bow, and two outside, the 



colours of the first being in reversed order, while the second 



was faint, and nearly white. Four of the rainbows were 



quite perfect, but the innermost of the three internal 



bows was partlv broken, only three-quarters being 



visible. About one-third of the extreme outer bow was 



visible. ^ ^, 



E. Newbery. 



Sidcot School, Winscombe, Somerset, November 6. 



Dangerous Mixtures. 



I SHOULD like to direct attention to the dangerous 

 nature of a mixture consisting of magnesium powder and 

 silver nitrate. 



When a small quantity (2 to 3 grams) of magnesiunv 

 powder is mixed with an equal bulk of powdered silver 

 nitrate in a metal dish, and then from the end of a long, 

 glass rod a drop of water is allowed to fall on the mixture 

 a slight explosion occurs, accompanied by a vivid flash. 



The unexpected violence of this reaction led to serio 

 burns in my own case. 



Mercuric nitrate when substituted for silver nitrate also 

 reacts vigorously with magnesium powder under the same 

 conditions, brown fumes, but no flash, being produced. 

 With barium nitrate the action is slight, heating only 

 appearing to take place. 



Harold Cal.\m. 



The University, Leeds, October 27. 





