372 



NATURE 



\Scpt. 5, 1872 



greater, in about the ratio of '275 to "isS, than it was close to the 

 limb ; these figures represciitini; approximately the amount of 

 polarisation respectively at ten minutes from the limb, and close 

 to it, the total light being unity. 

 We may therefore conclude that 



1. The corona is radially polarised. 



2. This polarisation increases as we recede from the limb. 

 The bright lines seen in the spectrum of the corona inform us 



that /(?/•/ of the light we receive from it is intrinsic, that is, tliat 

 the gases composing it are incandescent, and from their proximity 

 to the sun we should scarcely expect anything else ; yet this fact 

 in no way renders it impossible that much of tlie light we receive 

 from the corona should be rellected or scattered by minute par- 

 ticles of, perhaps, denser matter, probably incipient cloud, sus- 

 pended within it, as such particles are supposed to exist in the 

 earth's atmosphere, in order to account for the polarisation and 

 blue colour of the sky. This supposition, when we remember 

 that the temperature, and hence the amount of intrinsic light, 

 must decrease as we recede from the sun, would amply account 

 for the increase of polarisation with distance from the limb. 

 There are, however, two other causes which may be named as 

 adequate to produce this effect. Probably in reality the increase 

 is due to the three causes combined. 



\Vhen the plates were inclined so as to neutr.alise the corona 

 polarisation, I saw faint dark centred bands on the portion of the 

 moon's disc in the field. I did not observe any when the plates 

 were at right angles to the axis of the telescope, but I think I 

 should have noticed them had they existed ; so that although there 

 was a sensible amount of light on the moon's disc sufficient to 

 show bands when polarised by the glass plates, I do not think it 

 was perceptibly polarised itself. This would tend to show that 

 the light was reflected from the moon itself, and not from the in- 

 tervening atmosphere. G. K. Wi.NTER 



Erratum of the Errata, or, " A Few Millions" 

 I AM indebted to Mr. A. Cowper Ranyard, of London, for 

 calling public attention to errors existing in the illustrative 

 appendix to a research entitled Acoustical Experiments, &c. , 

 which article of mine the Editor of Nature honoured .with a 

 republication in his journal on May 9, 1872. 



The existence of these errors has been known to me since a 

 few weeks after the originil publication of my paper ; iDUt as 

 they did not affect in the least the subject proper of the research, 

 and would be apparent to any one who might take the trouble to 

 review the calculations, I allowed them to pass unnoticed, and 

 even now would not pursue the subject further had Mr. Ranyard 

 really corrected my errors ; but he has himself committed the 

 error of "A Few Millions" (the title of his communication*) 

 which he would attribute to nic when, in these words, he 

 undertakes the correction of my figures. " Taking the velocity 

 of light as 185,300 miles per second, and the wave-length 

 of Dj, as given by Angstriini, at o'ooo58g50 millimetres, gives 

 5.058,700,000,000,000 vibrations per second, or a little more 

 than fn'L' thousaiul iniUions of iiiillions, instead of a little less 

 than six hundred millions of millions vibrations per second, as 

 given by Dr. Mayer." The following is the correct calcula- 

 tion :— 



,, ., 208,212,000.000 mm. „ , ,, ,„ „,„ , 



185, OTO miles = -^-^ — ^ 505,870,000,000,000 



•0005895 mm. 

 and 5,058,700,000,000,000 (Mr. A. C. Ranyard's result) minus 

 505,870,000,000,000 (Mr. Mayer's result) gives Mr. Ranyard 

 4,552,830,000,000,000 tremors. 



Thus it appears that both Mr. Ranyard and myself commit 

 errors in simple arithmetic, but I am sure that our mutual friends 

 will not attribute them to v/ant of sufficient mathematical culture 

 to accomplish " a simple rule of-three sum." (A. C. R.) lie 

 that is without sin let him first cast a stone. I, however, do not wish 

 Mr Ranyard's errors in any way to extenuate my own greater 

 negligence which has disfigured the appendix of my paper, con- 

 taining, as it does, "some strange numerical errors, which 

 perhaps it will be well to point out, lest some of your readers 

 should make use of the numbers given at the end of the paper 

 without previously testing them, " (A. C. R.) I will therefore 

 ask my readers to substitute for the last paragraph under the 

 heading of " Quantitative Relations in the Experiments and 

 Analogical Facts in the Phenomena of Light," the following : — 

 " We will now examine the analogical phenomena in the case of 

 light. Let fork No. i, giving 256 vibrations a second stand for 



• Sec Nature, June 20. 



508,730,000,000,000 vibrations a second, which will be the 

 number of vibrations made by the ray Dj of the spectrum, if we 

 adopt 300,000 kilometres per second ai the velocity of light. 

 Then fork No, 3 will repreient 504, 750,000,000,000 vibrations 

 per second, which latter give a wave-length '0000048 millimetre 

 longer than that of Dj, and belongs to a ray removed from D,, 

 towards the red end of the spec rum, by eight times the distance 

 which separates D, from D„. We saw that fork No. 3, giving 

 254 vibrations a second, had to move towards the tar with a 

 velocity of 8734 feet to give the note produced by 256 vibra- 

 tions per second, emanating from a fixed fork ; so, if a star, which 

 only sends forth those rays which vibrate 504,750,000,000,000 

 times a second, should move towards the eye with a velocity of 

 2,442 kilometres, or 1,517 miles, its colour would change to that 

 given when Dj emanates from a stationary soda-dame." 



Alfred XL Maver 



Rev. John Ward on Atmospheric Germs 



This worthy was Vicar of Stratford-upon-Avon, from 1662 

 till his death in 16S1. He was a man of general knowledge, and 

 was specially skilled in the diseases of women and children. It 

 is not known that he obtained the archiepiscopal licence to prac- 

 tise physic, but he certainly practised the healing art, and he re- 

 cords his intention " to inquire whether a man may get of the 

 archbishop a licence to practise /<■;■ totaiii Aiii;liam !" His 

 diary, 1648-1679, is sensible and entertaining. It is chiefly 

 known as containing a notice of Shakespeare, with the only ex- 

 tant account of the cause of his death, viz., " a feavour " caused 

 by a carouse with Drayton and lien Jonson. The Diary is in the 

 Library of the Medical Society of London. It was edited by 

 Dr. Charles Severn, and published by Colburn, in 1S39. 



The following extract is remarkable : — 



" Venenum pestilens est congeries minlmarum animalcularum 

 per aerem volitantium, quK corpora humana per respirationem 

 aut poros subeuntes, eorum partes corrodunt et corrumpunt, ex 

 iiscjue ad alia corpora volitantes, sen ad alia quocunque modo 

 delatte, et quasi contagio propagator, etram ilia inficiuot, corro- 

 dunt, corrumpunt, sicut priora, e quibus evenerunt. 

 Supra fienum cubare noxium multis fecit, non solum in peste, 

 sed etiam in aliis morbis." 



Of course in pcste means " in the case ot the plague." 



C. 'M. Ingleby 



Coefficients of the Linear Expansion of Solids 



At the British Association which met list year in Edinburgh 

 I suggested a thcrinomdcr of translation which should record the 

 amount of the successive rises of temperature during the year. 

 For this purpose a body possessing great expansibility with a fine 

 needle point at its upper end, was proposed to be placed on a 

 sloping frame, and made of a material possessing small expansi- 

 bility, and protected from the changes of temperature, and having 

 its upper surface finely serrated. When the body expanded, its 

 upper end bearing the needle point would extend higher up on 

 the frame, and \vhen contraction commenced the projecting needle - 

 point would continue its hold of the teeth on the frame, prevent- 

 ing shortening at its upper end, so that the centre of gravity of 

 the mass would be raised. In this way the successive increments 

 of heat would be registered by successive creeps of the body up- 

 wards on the frame. 



It has occurred to me that the same principle might be ad- 

 vantageously adopted for measuring the linear expansion of 

 different solids. 



In order to double the readings for expansion, clamping screws 

 attached to upright rods fixed at the ends of the body would be 

 better than the needle point for detention during contraction, 

 which was proposed for the thermometer of translation. The 

 bar to be experimented on would be phaced on rollers m a vessel 

 containing water or steam of dilTerent temperatures. The screws 

 would be tightened at the lower end of the bar, and slackened at 

 the upper before expansion, and tightened at the upper and 

 slackened at the lower before contraction. After the contraction 

 had fully taken place, the bar would be again heated and again 

 cooled, and this process would be repeated until the total 

 amount of translation became easily measurable. Although the 

 amount of translation produced in any case by a single experi- 

 ment might be scarcely appreciable, yet we can by cumulative 

 repetition increase the amount of translation to any extent with- 

 out increasing the errors of observation, for a single final reading 

 is sufficient for the whole series of expansions however numerous 



