574 



NA TURE 



[Oct. 31, 1872 



just as it might permit of the wagging of the ears, or of tlie scalp 

 movements, which may be occasionally witnessed in those gifted 

 with such accomplishments. 



It is in the hope, then, that some one who has studied anatomy 

 from a mechanical stand-point may throw some light upon this 

 somewhat obscure matter, that I have asked a question wliich, 

 I trust, my be one not unworthy of the consideration of "philo- 

 sophical " anatomists. 



New University Club, Oct. 16 J. C. G. 



Magnetic Storm Oct. 14—18 



On the 14th of this month a magnetic storm commenced at 

 10.20 P.M., and lasted until II r.M. of the 18th. It was as re- 

 markable for the extent as for the duration of the disturbances. 

 The only lull in the storm was during the afternoon of the 

 1 6th. 



The general character of the perturbations was the same 

 throughout, consisting mostly of long movements of the needle 

 to and fro on either side of tlie mean position. There w.as a 

 very striking coincidence between the curves of the 15th, loth, 

 17th, and iSth during the morning hours, the maximum 

 westerly deviation having been attained at about 5 a.m. on 

 each successive day. During the afternoon of the 17th, the 

 greatest movement of the declination needle towards the west 

 was equal to that of the previous morning, whilst the oscillations 

 towards the north were greater than on the other days of the 

 storm. The movements of the vertical-force magnet were fre- 

 quently too great to be recorded on the photographic paper, and 

 this magnet was several times thrown off its balance. The 

 horizontal-force magnet was more violently disturbed at the 

 very commencement of the storm than at any subsequent 

 period. 



The remarkable coincidences that are now bemg discovered 

 between these magnetic disturbances and other impurcant 

 natural phenomena render it useful to draw attention to those 

 changes in the magnetic force of the earth wliich present any 

 feature particularly worthy of notice. The storm I am now re- 

 ferring to is on several accounts the most important that has 

 occurred since 1S67, and it is to be hoped that some practical 

 spectroscopist has had favourable weather during these few days, 

 as a magnificent array of solar prominences may not improbably 

 have rewarded his interesting labours. 



Stonyhurst Observatory, Oct. 23 S. J. Pkrry 



Circular Rainbow 



Being, in company with a friend, Mr. Hall, on the east pe.ak 

 of the Berceau {3,640 ft.) on the 25th inst., a circular rainbow was 

 visible at 2.30 p.m. upon the upper surface of light white clouds 

 that drifted from S. up the rocky valley. whicli was E. of where 

 we stood — though the true wind was W. and moderate. The 

 sky was almost of the richly dark Italian blue, across which a 

 few clouds (cirrus) slowly passed. 



When first seen the diameter of the outside of the circle was 

 10", but it increased gradually up to 15°. The colours of the 

 "bow," which was somewhat less than i" in width, — were the 

 same as in the common rainbow, and very vivid. When we were 

 a few yards apart, each saw only his own figure within the circle, 

 large and well defined, so that the movement of an arm became 

 visible. Before long the shadow of the mountain on which we 

 stood invaded the lower portion of the circle, depriving it of its 

 colour, but not always destroying its continuity ;— and my I'gure 

 remained comiilete even v.'here the continuity was destroyed. 

 Light clouds passed across the sun, causing a partial, rarely a 

 complete, disappearance of this most beautiful phenomenon, 

 which we watched with great interest for twenty-si.K minutes — 

 how long it had existed before 2.30 I know not. 



M. MOGGRIDGE 



Earth Currents and Sun-spots 

 In the last number of Nature there appears a letter 

 from Mr. W. H. Preece respecting the recent occurrence 

 of electric storms of con>iilerable intensity ; and in connec- 

 tion with this interesting subject it may be worth while re- 

 lating that the solar s|iots"h,ive lately (that is to say, during tlie 

 last few weeks) been larger than usual. One of them attained 

 great proportions, and was distinctly visible to the unassisted eye 

 (on October 15) through a fog which partially obscured the sun's 



intense light. On the date mentioned this spot had completed 

 about one-half of its transit across the solar disc, and it is remark- 

 able that on the same day the electric storms attained their maxi- 

 mum, and "the interruptions to business were serious," as 

 remarked by your correspondent. The spot referred to was not 

 so large as several which appeared during the two preceding 

 years, but exceeded in magnitude any of those which have come 

 under my observation during the present year. It disappearetl 

 from the sun's western edge on .about the 21st of October ; but 

 just previously to this the spot had been considerably smaller, 

 and showed indications of dissolution. The spots now visible 

 on the solar surface are not very conspicuous ; there are, how- 

 ever, two visible of the larger class — -one of these is situated in 

 the north-east quadrant, and the other in the south-east quadrant, 

 and they are situate at about the same distances from the limb. 

 Between these spots there were yesterday two small ones percep- 

 tiljle running parallel with the equator. 

 Bristol, Oct. 2S William F. Denning 



Measurement of Faint Spectra 



May I suggest, as a supplement to Mr. Capron's clever 

 arrangement for spectral measurement, a method which I have 

 found useful with faint spectra. It is that a part of the slit 

 should remain fixed, while the upper or lower half, or the middle 

 only, should be movable. In this way two images of the spec- 

 trum are formed, one of which may be made to move over the 

 other like a vernier ; and thus any line may serve as an index, 

 when, from want of light, it would be impossible to see the brass 

 points. We obtain in this w.ay many of the advantages of Z611- 

 ner's reversion spectroscope. 



With such an arrangement, and with an embossing edge 

 attached by a spring to the movable slit, so as to register on a 

 card when pressed, I have succeeiled in making several tolerable 

 measurements of tlie faint auroral bands, which it was difficult to 

 perform by direct comparison. It is, of course, necessary to have 

 at least one line of known position in tlie field. 



North Shields, Oct. 22 Henry R. Procter 



Merrifield on the Deviation of the Compass 



Will you kindly pardon ray again troubling you with an 

 explanation ? 



Last week, seeing what I considered a harsh review of my 

 Utile book, in Nature for Oct. 17, I, in the midst of my work 

 and the heat of the moment, penned a reply to my reviewer, 

 without thinking more of the matter. To-day, whilst giving a 

 lesson on the subject to a pupil, I saw my error ; and I beg to 

 plead guilty to that " looseness" which has led to inaccuracy in 

 the passage quoted from page 5-- Instead of "deviation" I 

 meant, and should therefore have said, " Vertical iron shows the 

 same indirect magnetic force," &c. , and to my class I have 

 always used these words. I now tender my apology to my re- 

 viewer for my hasty letter, and beg to thank him for pointing out 

 this "looseness and inaccuracy." I trust you will make this 

 letter as public as my last. John Merrifield 



Navigation School, Plymouth, Oct. 26 



Rainfall in Bombay 



As it may interest some of the readers of Nature to know the 

 amount of rain which fell on one occasion during the heavy mon- 

 soon rains which recently occurred at Bombay, and which I 

 regret to see in your Notes had so disastrous an effect upon the 

 library of the Asiatic .Society, I quote the following from a 

 letter which I have just received from my friend Mr. C. Chambers, 

 F.R.S., Director of the Colaba Observatory, dated loth Sept., 

 1S72. 



"Just a week ago we were treated to 7"20 inches of rain in two 

 hours, which is nearly twice as heavy as I have known before, 

 i.f., had personal experience of." 



In order that we m-y form some idea of the enormous amount 

 of the downpour, we must imagine the whole rain which has 

 fallen in this neighbourhood since June 8, to have been concen- 

 trated in the time named ; or, perhaps, better still, to suppo. e that 

 the heaviest p.irt of the shower which fell about half-past twelve, 

 on the 3rd inst., and lasted for seven minutes, had continued for 

 two hours. 



Mr. Chambers was some time ago much troubled by the 



