434 



NATURE 



{Sept. 26, 1872 



Doubtless it is not necessary, but the obligation is the same ; 

 and a mistake into which Prof. Young has fallen is open to 

 others. 



The mip which he wants— to be based on inverse wave-length 

 or rapidity of vibration or pitch— is, I believe, in course of con- 

 struction by Dr. lluggiiis, to whom, and not to me, is due, I 

 think, the first idea and the proposal. Prof. Young has probably 

 associated my name witli it through a lecture delivered by my 

 brother at Glasgow, in 1S69, in which it was advocated. 



I also wish to acknowledge that I was not aware of the fact 

 which has now been so decidedly sta'ed, that tlie coronal green 

 line is certainly //v;<-//<-,7//i' identical in position with 1474 (K), 

 as tested by direct comparison. Indeed, I was ignorant that such 

 a comparison was possible, having supposed that the line in 

 question was only visible during eclipse. I ought, of course, to 

 have referred to Prof Young's " Preliminary Catalogue," and 

 probably should have done so had I bee.i in a house instead of 

 in a tent, a few score of miles from the nearest station. But in 

 truth it did not occur to me that there could be any certainty 

 alraut the position of a line which, as a coronal line, had never 

 been hxed by measurement. I may now venture to ask. What 

 guarantee was there that No. 31 of the " Preliminary Catalogue " 

 was "the coronal line," anterior t) the Dodabetta measure- 

 ment? I do not question it now, but I should like to know if 

 the presumptive identity is supported by any characteristic 

 difference between that line aud those which are presumibly 

 due to the chromosphere. There is still a link wanting. 



However, admitting the identity, and therefore the accuracy 

 of the assigned position, we may still believe what Prof Young 

 says he would be glad to see proved, that " the apparent coin- 

 cidence (with the iron line) is merely a very close juxtaposition." 

 More than this : even were a very much higher dispersive power 

 to show no resolution of the identity, should we not still be in 

 nearly the same position as to aay inference to be drawn there- 

 from? Evidence of physical relation between metals which 

 present one or more lines common to both spectra may, indeed, 

 eventually be shown (by the improbability of so frequent an 

 accidental concurrence) to amount to proof. But this must be 

 a prior step. To conceive it taken, and then to apply the like 

 reasoning by analogy to the case of the single coronal line tally- 

 ing with an iron line, seems to me speculation of the second 

 order. Undoubtedly it would be matter for congratulation to be 

 relieved from the liability to temptation of this kind by definite 

 disproof In the meantime, I cannot but regret that Prof Young 

 has half neutralised the good of a plain disavowal of belief in the 

 ferrous interpretation of the coronal green line, by hazarding the 

 query whether it may not "turn out" to be quasi-ferrous. 



I am sorry— to return to the subject of nomenclature— that 

 your respondent does not agree to my oljjection to " D3." Is it 

 not plain that such a designation is haphazard ? The association 

 of idea is with Dj due to sodium, instead of with the origin or 

 source of the line. It tells nothing beyond the position, roughly, 

 in the spectrum, by reference to a position which we happen to 

 be familiar with, but with the occupant of which it has no con- 

 nection otherwise. The name, in short, has no foundation in 

 principle ; and that, I apprehend, is a lack of the first requisite 

 in a scientific name. 



The objection to'Greek alphabet letters is of a different charac- 

 ter, but not less easily answered. It is very true that, through 

 the exertions of Prof Young and others, " the whole Greek 

 alphabet would not suffice to name one in three of the lines " 

 already known ; but it would nevertheless suffice (as in the some- 

 what analogous case of the stars) "to express as many as the 

 memory would require to hold." There is ample precedent. 

 The principal lines of the elements, like the principal stars of 

 constellations, are known to some extent by Greek letters ; and 

 as for the difficulty in respect of order, there Avas a time when 

 the "lucid" stars, though very many in number, and having no 

 very clear claims to precedence, w-ere only known individually 

 by personal names. Yet no sooner did a Bayer rank and name 

 them according to apparent brilliancy, by Greek letters (to say 

 nothing of the Roman), than the advantage of a fixed nomen- 

 clature was recognised and his work accepted ; although obser- 

 vation must have shown that the assigned order was not always 

 strictly correct. So would it happen now if, the lines having 

 been lettered, further knowledge should show that the established 

 precedence was not quite all that could be wished. The evil of 

 slight incoiTeclness of this kind would be felt to be trilling conr- 

 pared with that which would result from an unsettling of a 

 nomenclature established solely for convenience and involving no 

 theory. 



This would not prevent nor conflict with, neither would it 

 render unnecessary, a far more extended tabulation depending on 

 refrangibility. On the contrary, the want of such a classification 

 and means of in lication would be felt as soon as precise tabula- 

 tion should come to be undertaken. In Kirchhoff's solar chart 

 we have, graphically, something like what is wanted in a much 

 more general, numerical, and tabular form — an example of a 

 catalogue of lines. Charts are very useful, but not most handy ; 

 and they are not susceptible of such ready improvement and ex- 

 tension. The accumulation of results of spectroscopic research 

 must sooner or later take the form of a catalogue of lines, from 

 all sources, arranged in order of refrangibility ; designating indi- 

 vidu.als (for special reference) where possible, according to their 

 parent element or compound, the'r physical source, their cosmical 

 habitat, or other characteristic and distinguishing indication, 

 implied under the system of nomenclature which may be adopted ; 

 upon which would follow such details as to character (including 

 intensity, width, definition, complexity, variability, &c. &c ) as 

 present knowledge or future research may represent as suitable 

 nnteriil for incorporation. 



So long as spectroscopic analysis is content to remain in its 

 earhest stages — and it must be allowed to be still in its infancy, 

 though a giant from its birth — the student and experimentalist 

 may to a very considerable extent learn by heart or by practice 

 such spectra as he needs ; but this can never suffice for all pur- 

 poses. Accumulation is continually going on, and products 

 must be stored. Let that be once acknowledged and the task 

 attempted, and it must follow that, no m.atter how rigorous and 

 precise may be the system of tabulation, there will be not only 

 room, not only gain, but a positive necessity for an intelligible 

 use of that kind of descriptive indication which is only to be 

 found in scientific classification and nomenclature. 



A general catalogue such as I contemplate would command, 

 if compiled with even moderate knowledge and care, a very 

 general acceptance. Unquestionably it would b3 extended, 

 modified, improved upon, by subsequent work ; but, so far as 

 nomenclature is concerned, it would probably undergo but slight 

 alteration — the less the better. It would form a basis on which 

 any number of special catalogues might rest, without interfering 

 with its permanence as a catalogue of reference. 



I dj not pretend to say that the task is a simple one; quite 

 the reverse. But, then, all the more honour to whoever accom- 

 plishes it. J. Herschel 



Bangalore, July 29 



Jeremiah Horrox 



I OBSERVED in a number of Naix're some three weeks ago 

 an inquiry relative to J. Horrox, the astronomer. My wife is 

 descended from Horrox, and I knew that one of her friends had 

 his life, but have not been able to find it till now. The book 

 has just been sent to me here. 



The Rev. Jeremhah Horrox was born in Toxteth Park, near 

 Liverpool, in 1619, and died in 1641, aged 22. 



The life is by the Rev. A. B. Whatton, published by Wer- 

 theim, Macintosh, and Hunt, 24, Paternoster Row, 1859, and 

 includes a translation of his discourse on the Transit of Venus. 



Henry Holid.w 



Muncaster Castle, Ravenglass, Carnforth, Sept. 20 



Millions of Millions 



Why do not Messrs. Ranyard and Co. adopt the late Ben- 

 jamin Gompertz's most convenient notation of prefixing a circle 

 to the first significant figure, or suffixing a circle to the last sig- 

 nificant figure having therein a digit for the number of zeros 

 employed? 



Thus: -QyiS is "00000718 



And 7lS(j!) is 718000000 



74, Offord Road, N., Sept. 17 



S. M. Drach 



Analogy of Colour and Music 

 In Nature, No. 150, p. 393, a letter from Mr. G. C. Thompson 

 is headed " Correlation of Colour and Music." As this letter re- 

 fers to a p.aper of mine published some time ago, permit me just 

 to say that Mr. Justice Grove has in your journal objected to the 

 use of the word " correlation " employed in this sense. En- 

 tirely coinciding with the opinion of the eminent parent of this 



