420 



NATURE 



[FlJBRUARY 28, 1901 



will unite. At the moment of union the form of the vortex is 

 very unstable, being an extreme case of the vibrating elliptical 

 ring. It at once springs from a horizontal dumb-bell into a 

 vertical dumb-bell, so rapidly that the eye can scarcely follow 

 the change, and then slowly oscillates into the circular form as 

 shown in Fig. 6. This same phenomenon can be shown with 

 two paper tubes held in opposite corners of the mouth and 

 nearly parallel to each other. The air in the room must be as 

 still as possible in either case. R. W. Wood. 



University of Wisconsin, Madison. 



Dust-tight Cases for Museums. 



The new geological museum now being erected here will 

 have high windows and a long south aspect. The effect of this 

 will be that the sun will fall suddenly on glazed cases and as 

 suddenly pass off them, thus by the expansion and contraction 

 of the air causing dust-carrying currents to force themselves 

 through every chink. From this cause it costs about three times 

 as much to keep cases and specimens clean on the side exposed 

 to the sun as it does in the shaded part of a museum. This 

 may be obviated by elastic diaphragms (which would hardly 

 allow sufficient movement for such large cases as ours) or by 

 small sliding shutters packed with cotton-wool something like 

 Tyndall's respirators. 



Can any of jour readers refer us to museums in which such a 

 system has been tried, or give us any advice on the subject before 

 our cases have been built ? T. McKenny Hughes. 



Woodwardian Museum, Cambridge, February 19, 



Audibility of the Sound of Firing on February i. 



Sir W. J. Herschel's letter is very interesting, and I should 

 like to make a few remarks upon it. To begin with, it must, I 

 think, be granted that the discharge of the guns was almost 

 simultaneous. The special correspondent of the Times on board 

 the J/a/if^//c says, "and then simultaneously all the vessels in 

 the long lines joined in, like the tolling of the passing bell." 

 And the special correspondent of the Times at Osborne says : 

 " A minute's interval . . . again the quick red flashes down the 

 line, and again the dilatory roar." But why do we find the full 

 minute's interval at Eastbourne, and three reverberations a 

 minute at Oxford ? Assuming that there was no firing at 

 Windsor, the reason, I think, must be sought for in the very 

 different character of the roads the sound had to travel over to 

 reach these respective places. In our case the road was all 

 over the sea with the exception of a few miles of low-lying land 

 at Selsey Bill. On the other hand, to reach Oxford the sound 

 would be greatly impeded by the contour of the land, to say 

 nothing of some possible echo from the high ground of the Isle 

 of Wight. Independently of Sir W. J. Herschel's letter, I 

 have grounds for thinking that the sound followed the course of 

 the valleys, and it is possible that the separate reports per 

 minute emerged by as many different channels of passage and of 

 echo. To have received the sound in a straight line, that is to 

 say, to have been high enough to have seen the ships at Spit- 

 head, one would have had to have been at an elevation of some- 

 where about 2800 feet at Eastbourne and 3200 feet at Oxford. 



Eastbourne. H. D. G. 



Influence of Physical Agents on Bacteria. 



In your report of Dr. Allan Macfadyen's lecture on the 

 influence of physical agents on bacteria (p. 359), I should like 

 to call attention to one point. Dr. Macfadyen suggests that 

 since phosphorescent bacteria regain their power of emitting 

 light after being cooled to the temperature of liquid hydrogen, 

 it may be the case that life is not dependent for its existence on 

 chemical reactions. Because, says he, at the temperature of 

 liquid hydrogen, e.g. -250°C., all chemical reactions are well- 

 nigh, if not absolutely, at a standstill, if life were dependent on 

 chemical reactions for its continuance, at that low temperature 

 life would be destroyed. I would submit that this is a case 

 of non sequitur. It appears exceedingly probable that the 

 action of excessive cold in suspending and stopping vital 

 phenomena, while not destroying the capacity of organisms to 

 resume their vital activities, supports the prevalent view that life 

 is dependent on chemical processes. For may it not be that 

 excessive cold, while preventing the vital processes from taking 

 place, by no means alters the chemical constitution of the com- 



plicated molecules, the interactions of which normally produce 

 vital phenomena, and leave these molecules, which one may 

 call biogens or anything else, in exactly the same state as they 

 were immediately before the onset of excessive cold, ready as 

 soon as the conditions become suitable once more to resume 

 those vital processes which are known as metabolism. 



As an illustration of what I mean I will quote a case of in- 

 organic phosphorescence. It is well known that phosphorus is 

 slowly oxidised in air and emits light at the same time. This 

 reaction takes place when the air is at the pressure of the 

 atmosphere, and the partial pressure of the oxygen is one-fifth 

 of an atmosphere. If, now, the pressure of the air be made 

 equal to five atmospheres, or if the air be replaced by pure 

 oxygen at a pressure of one atmosphere, in both of which cases 

 the pressure of oxygen is five times as great as before, the oxida- 

 tion ceases and the phosphorescence vanishes. But this is only 

 because the conditions are unsuitable, the constitution of the 

 phosphorus and the oxygen is unaltered, and as soon as the 

 pressure of the oxygen is lowered the phosphorescence begins 

 once more. In both cases, the bacteria and the phosphorus, 

 the action of the physical agent — in the one case cold, in the 

 other pressure — is merely to render the conditions unsuitable for 

 the appearance of the phenomenon, and not to destroy the pos- 

 sibility of its subsequent revival. H. D. D. 



Balliol College, Oxford, February 10. 



NO. 1635, VOL. 63] 



Malaria and Mosquitoes. 



I WAS Stationed in Karachi, Sind, for more than twenty years. 

 There was undoubtedly a strong belief with the Indians that the 

 disturbance of ground for building led to fever; building opera- 

 tions may be estimated by the fact that I went to a city of 

 45,000 inhabitants and left 130,000. Not long before I left, the 

 ground of the native town was disturbed by the installation for 

 the first time of a system of underground drainage. I think, but 

 am not sure, this was followed by an outbreak of fever. 



Qua mosquitoes, may there not be a distinction between 

 malarious and ordinary fever. F. C. Constable. 



Wick Court, near Bristol, February 24. 



Snow Crystals. 



After the recent heavy snow in this district, the slight fall yes- 

 terday afternoon did not, at first, attract much attention, appear- 

 ing like sleet to the casual observer. It proved, however, to be 

 of an unusual character, consisting chiefly of beautifully-formed 

 single crystals. It was remarked that " it was snowing stars ; " 

 and the ground became covered with myriads of them, varying 

 in size, some being a quarter of an inch in diameter. These 

 " frost flowers " appear tohave been common enough in Tyndall's 

 Alpine experiences, but are, I imagine, rarely seen in England 

 upon this scale. The thermometer registered 30° Fahr., and it 

 would be interesting to know if this phenomenon was peculiar 

 to the High Peak district, and what are the conditions conducing 

 to such a display. Wm. Gee. 



Buxton, February 19. 



A ''NEW STAR" IN PERSEUS. 



"\ 1 rE have received the following : — Edinburgh Circular ^ 

 ^^ No. 54. A new star was discovered in Perseus, 

 by Dr. T. D. Anderson of this city, on February 21, 

 i4h. 401T1. G.M.T. The star was then of the 27 magni- 

 tude, and shone with a bluish-white light. Dr. Anderson 

 gave as its approximate place for igoro : — 



R.A. 3h. 24m. 25s. Decl. -I- 43° 34'. 



At 6h. 58m. G.M.T., on the 22nd, the undersigned 

 estimated the Nova as o"3 magnitude brighter than 

 a Tauri, and at 8h. lom. considered it equal to Procyon, 

 which it closely resembled in colour. 



On the 23rd, at 8h. lom. G.M.T., Dr. Halm and Mr. 

 Clark found the new star o"2 magnitude brighter than 

 Capella. 



A direct-vision prism on the 6-inch refractor showed 

 nothing beyond a perfectly continuous spectrum. With 

 the large Cooke spectroscope on the 15-inch equatorial 

 the first impression was the same as with the smaller 



