September 30, 1909] 



NA TURE 



395 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with th& writers of, rejected 

 manuscripts intended for this or any other part o/ Nature. 

 No notice is taken of anonymous commtinications.] 



Visibility of Halley's Comet. 



The discovery of Halley's comet at a time so far pre- 

 ceding the date of perihelion passage adds another proof 

 of the great capacity of the photographic method. The 

 interesting point to many observers is as to when the 

 comet will become visible to them as a telescopic object. 

 This must, of course, depend in a large measure upon the 

 diameter of their glasses and on their powers of vision. 

 .■Xfter the present moon has left the sky, say during the 

 second week in October, the comet ought to have increased 

 in light sufficiently for it to be observed in a 12-inch 

 telescope. The calculated magnitude of the comet will be 

 14J on October 15, and its distance from the earth about 

 230 millions of miles. Its apparent position will then be 

 five degrees west of 7 Geminorum, and near 72 Orionis. 

 On October i5 the comet will be just two degrees south of 

 71 Orionis (mag. 5-5), and ought to be visible as a very 

 faint nebulosity, especially if the night is good. The 

 transparency of the air has an important influence on the 

 perception and aspect of faint comets and nebulse, for a 

 really suitable sky will enable objects to be glimpsed which 

 are utterly invisible on bad nights when there is diffused 

 light, thin cloud, mist, or fog prevalent. The comet will 

 be visible in an excellent position nearly all night during 

 most of the winter, but will continue small and faint until 

 it blazes out next April. W. F. Denning. 



The Presence of Haemoglobin in Invertebrate Blood. 



May I make use of your columns to correct a statement 

 in my article on Crustacea in vol. iv. of the " Cambridge 

 Natural History," which I am afraid may seriously mis- 

 lead the reader? Referring to the alleged presence of 

 haemoglobin in the blood of Branchipus and Daphnia, I 

 have stated in a footnote on p. 30 that the fact that the 

 red blood of I.ernanthropus has been proved not to con- 

 tain haemoglobin throws doubt on the reality of its presence 

 in the other two animals. At the time of writing I was 

 not aware that the authority on which the presence of 

 lijemoglobin in Branchipus and Daphnia rested, and 

 I was inclined to impugn, was Sir Ray Lankester, who, in 

 the late 'sixties and early 'seventies, published a series of 

 researches which laid the foundation of a comparative 

 knowledge of the distribution of haemoglobin and similar 

 respiratory pigments in the animal kingdom (see especially 

 Proc. Roy. Soc, vol. xxi., December, 1872, p. 70). After 

 reading these articles it is clear to me that Sir Ray 

 Lankester's statement as to the presence of hfemoglobin 

 in the blood of Branchipus and Daphnia, resting as it 

 does on careful microspectroscopic examination, is quite 

 unaffected by what may or may not be the case in 

 Lernanthropus. so that 1 can only withdraw my footnote 

 with many apologies to him and to readers of the " Cam- 

 bridge Natural History." With regard to Lernanthropus 

 and its allies, small Crustacea parasitic on fish and mussels, 

 which possess a closed vascular system containing a red 

 fluid, there is still some doubt. Van Beneden, who dis- 

 covered Lernanthropus in 1880, states (Zoologischer 

 Anzeiger, Bd. iii., p. 35) that he examined the blood 

 spectroscopically, and found the oxyhjcmoglobin lines. 



More recently Dr. Steuer (Arbeiten Zool. Inst. Wien, 

 vol. XV., p. 14, 1003) sent numerous specimens of an 

 allied form, Mytilicola, to Prof. R. von Zeynek in Vienna, 

 who came to the conclusion that the blood did not contain 

 liaimoglobin, since (i) with glacial acetic acid and sodium 

 chloride no ha'min crystals were obtained ; h) after reduc- 

 tion with potassium cyanide and ammonium sulphide, the 

 characteristic reduced ha-moglobin lines were not formed ; 

 (3) there was no haemochromogen reaction. 



Curiously enough, we are not told whether the simple 

 examination of the blood gives the oxyhannoglobin lines, 

 as Van Beneden stated, or not, so that we are left in doubt 

 whether Van Beneden was altogether in error or the red 



NO. 2083, VOL. 81] 



substance in the blood of Lernanthropus possesses one of 

 the properties of hemoglobin but not the others. The 

 matter being in this unsatisfactory state, it is very 

 desirable that someone, to whom the opportunity is offered, 

 should re-investigate the blood of Lernanthropus. 

 New College, Oxford. Geoffrey Smith. 



MAGNETIC STORM OF SEPTEMBER 25. 



DR. CHREE, F.R.S., has sent us the following 

 communication on the above : — 



The magnetic storm of .September 25 exhibited the 

 rapid oscillatory movements that are usually associated 

 with the appearance of aurora. .As recorded at Kew, 

 the storm commenced suddenly at about 11.43 a.m. 

 During the next nine hours there was an almost unin- 

 terrupted succession of large oscillatory movements in 

 the magnetic curves, especially those of declination 

 and horizontal force. The storm was of comparatively 

 short duration, no movements of any great size being 

 recorded after 8.30 p.m. on September. 25, and by 

 I a.m. on September 26 little trace of disturbance was 

 left. When the storm was at its height the oscillatory 

 movements were so rapid that the record left on the 

 photographic, paper was frequently too faint to show 

 minute details, and the limits of registration were at 

 times exceeded. 



.\t the commencement there would appear to have 

 been an exceedingly rapid oscillatory movement of the 

 declination needle, after which the needle moved to 

 the east continuously for about 15 minutes. After 

 the first 12 minutes, during which a movement of 

 72' was recorded, the trace got off the sheet, so that 

 the full extent of the easterly drift is not shown. 

 After a few minutes' absence the trace reappeared, 

 but, after some oscillatory movements of the needle, 

 the trace got off the sheet again on the same side as 

 before at about 12.12 p.m., and remained off on this 

 occasion for nearly 40 minutes. During the whole of 

 this time the needle pointed at least 70' — at times, 

 probably, a good deal more — to the east of its normal 

 position, .\fter coming on the sheet about 12.52, the 

 trace exhibited some minor oscillations superposed on a 

 rapid drift across the sheet. The entire width, repre- 

 senting 2° 7', was crossed in less than half an hour, 

 and the trace at about 1.20 p.m. got off the sheet on 

 the opposite side. The needle then pointed about 1° to 

 the west of its normal position. Between 1.20 p.m. and 

 8.^0 p.m. there were a number of large oscillations, 

 movements of 40', 60', or more, now east, now west, 

 taking place in the course of a few minutes. The 

 largest of the rapid oscillations clearly shown took place 

 between about 8.7 and S.22 p.m., a westerly move- 

 ment of qS' being followed by an easterly movement 

 of 84'. The disturbance shown by the horizontal-force 

 curve was no less remarkable. The commencing 

 movement at 11.43 ^-"i- ^^'^nt beyond the lower limit 

 of registration, a "fall of 430 y taking place in about 

 10 minutes. .At this time "the trace was off the sheet 

 for only about 5 minutes. After reappearing it showed 

 large oscillations. By 12.53 P-"i- •' ^'^'^ crossed the 

 sheet to the other side, the change of force during 

 one period of 13 minutes being no less than 625 7. 

 The trace was off the sheet continuously from 3.55 to 

 5.10 p.m., the horizontal force during the whole of 

 this time exceeding its normal value by more than 

 300 7. Except when off the sheet, the trace showed 

 continuous large oscillatory movements during the 

 whole afternoon. The largest clearly shown was 

 partly synchronous with the large declination oscilla- 

 tion near 8 p.m. already described; it consisted of a 

 rise of 520 7 and fall of 710 7, all in the course of 

 17 minutes. 

 The declination range, 2° 7', and the horizontal-force 



