126 



NA rURE 



[Df.cember IO, I 89 1 



formation. And if the people in the Dog Star chose to define 

 four as I f I + I, the so-called " necessary truth " would not 

 even be true ! Again, we do not ' ' recognize that what we know 

 *is ' cannot at the same time 'not be,' " v\e define it to be so. 

 To know that anything "is," is indeed to possess real know- 

 ledge ; but in order to conclude that therefore it cannot "not 

 be," we require no further knowledge, except as to the meanings 

 of the words employed in the argument. The " law of contra- 

 diction " never tells us whether anything "is" or "is not." 

 It only tells us that the terms "is" and "is not" are not 

 applicable to the same thing. This is part of the definition of 

 the terms. If anyone chooses to say a thing both " is " and " is 

 not," there is no law against his doing so, only if he does so he 

 is not talking the Queen's English. Dr. Mivart is wrong in 

 speaking of the "objective absolute validity of the law of 

 contradiction." Its validity is not only not objective at all, hut 

 even subjectively it is not absolute, but depends on the arbitrary 

 meanings assigned to its terms. It is exactly on a par with the 

 assertion that at chess one king cannot give check to another. 



Edward T. Dixon. 

 Trinity College, Cambridge, November 29. 



The Koh-i-Nur. 



Absence from home and pressing business since my return 

 have delayed my sending a reply to Prof. Maskelyne's second 

 article upon the above subject (Nature, November 5, p. 5). 

 So far as I can discern Prof. Maskelyne's primary object in 

 writing these articles, it is to endeavour to maintain the hypothesis 

 put forward by him many years ago ; and with this object in 

 view he has made a number of statements, from which I have 

 culled not a few that may be ranged under either of two heads 

 — firstly, those which I believe can be shown to be distinctly con- 

 trary to the evidence ; and secondly, those which, if not directly 

 contradicted by the evidence, are quite unsupported by it. 

 In my first reply I gave samples of these statements which 

 afforded perfectly clear issues, and as these have been un- 

 answered, it is useless to refer to others in detail at present. 



Some readers of what has already been written have ex- 

 pressed to me their regret that finality has not been attained 

 by this discussion. For my own part I have a feeling of 

 sincere regret at any additional confusion being introduced into 

 the subject. Some of the statements referred to may, unless a 

 warning be given, be quoted in the future, as others have been 

 in the past, by writers who may not have the means or may not 

 be willing to take the trouble to refer to the original authors. 



There are several references in Prof Maskelyne's last article 

 ■to authors with whose writings I have considered it to be my 

 business and duty to make myself familiar. I possess their 

 works, and of one of them I have recently published a detailed 

 commentary, while of another I have a commentary in course of. 

 preparation. Among these authors are Garcia de Oria and 

 Chappuzeau, and Prof. Maskelyne's remark ■; lead me to con- 

 clude that he has not a very intimate acquaintance with their 

 writings and with those of some of their contemporaries. From 

 internal evidence it is practically certain that at the time Garcia 

 wrote his book he had not visited the .VTogul's Court, and could 

 not, therefore, have seen his jewels, though, for the sake of 

 argument, Prof. Maskelyne suggests he had. As for the dis- 

 credited Chappuzeau, whose malicious statements are quoted 

 without their refuta ion, I need only say that Prof. Joret's 

 investigations have cleared Tavernier of the charges of plagiar- 

 ism, &c., which were made against him, and they have further 

 ■disclosed the fact that his own original manuscript documents, 

 from which the " Travels " were prepared, are still extant (see 

 preface to the second volume of my edition of the "Travels "). 



Now, as to the De Boot mistake, to which Prof Maskelyne 

 again refers as though it had an important bearing on the 

 subject, it is the case that Mr. King, in a footnote, pointed out 

 the error in De Boot's quoting as from Monardes. The footnote 

 does not occur in Mr. King's account of the diamonds, but 

 elsewhere. When I wrote, I had Prof. Maskelyne's quotation 

 {Edinbtirgh Review), as from Mr. King, before me, and thus I 

 was for the moment misled as to the extent of Mr. King's 

 knowledge. Seeing, then, that it was Prof Maskelyne's mis- 

 quotation which misled me, his not having accepted my invita- 

 tion to explain, coupled with his crowing over me for having 

 ■been misled (by his own words), is one of the most extraordinary 



features in this controversy. Two years ago I annotated my 

 original paper with the remark that Mr. King had noticed the 

 mistake of De Boot about Monardes, but it was then too late 

 to correct the press. 



The confusion which has most unfortunately been introduced 

 into this subject by authors has now,- it is to be fervently hoped, 

 culminated in the publication by Prof. Maskelyne of a figure of a 

 huge mounted jewel, which, going much further than his pre- 

 vious reference to it might have led one to expect, he labels 

 "The Mogul." What the authority may be for this sketch, 

 we are not clearly informed ; all, apparently, that can be 

 said for it is that " it speaks for itself" I cannot understand 

 how Sir John Malcolm can be responsible for it, at least as it is 

 labelled, because I know what he has published about the 

 Shah's jewels, especially the Darya-i-Nur and its companion the 

 Taj-e-mah. Kerr-Porter, Eastwick, and others who have de- 

 scribed the Shah's jewels, make no mention of the existence of 

 any such stone as this figure represents. 



"It speaks for itself" ; and I must venture by two alternatives 

 to hazard an interpretation of what it says. Firstly, the amor- 

 phous-looking mass may be intended to represent some uncut 

 stone, possibly a ruby ; but why should it be the Mogul's 

 diamond, which is known to have been cut ? Secondly, it seems 

 to be more probable that the figure may have been taken from 

 a native sketch which originally professed to represent, but 

 greatly exaggerated the size, and omitted the facets, of the 

 Jioh-i-Nur. Prof Maskelyne says it was accompanied by two 

 other stones in the same mount : so was the Koh-i-nur (see the 

 copies of the original model in the Tower and in several public 

 museums). The character of the mount is somewhat similar to 

 that in the Hon. Miss Eden's sketch of the Koh-i-Nur. This is 

 all that, as it appears to me, can be legitimately deduced from 

 this figure which has been left " to speak for itself" 



As to Prof. Maskelyne's own sketch of the Koh-i-Nur, I 

 thank him for it, because I think it may perhaps serve to aid 

 readers who have not seen the original in accepting the hypo- 

 thesis put forward by me, that it had been mutilated after 

 cutting. 



Through the kindness of Mr. L. Fletcher, F.R.S., Keeper of 

 the Minerals in the British Museum, I have recently had an 

 opportunity afforded me of seeing the original plaster model of 

 the Koh-i-Nur, and of comparing it with a glass model similar 

 to the one upon which my remarks as to the mutilation were 

 based, and I find them to be identical in form and all essential 

 details. V. Ball. 



Dublin, November 13. 



Pfaff's 



AUgemeine Geologic als Exacte 

 Wissenschaft." 



NO. II 54. VOL. 45] 



In this work (Leipzig, 1873) there is a speculation (on p. 162) 

 that in early geological times the carbonic anhydride, while yet 

 free on the surface of the earth, was sufficient in quantity to 

 exert a pressure of 356 atmospheres. If this had been the 

 condition of things at any time when the surface temperature 

 was below the critical temperature (30° '9 C), it follows that 

 abundant liquid carbonic anhydride flowed over the surface of 

 the earth, or floated upon the seas ; unless it be supposed, 

 which is not probable, that this quantity could be held in solu- 

 tion in the water. Other very important and interesting effects 

 are also involved. The statement of the 356 atmospheres has 

 been quoted without question by so high an authority as Dr. 

 Irving in his " Metamorphism of Rocks." 



Pfaff's result, however, is based on a statement of Bischof's 

 (as quoted by Pfaff ), that the calcium carbonate of all formations 

 would suffice to cover the surface of the earth to a depth of 

 1000 fiisse. Pfafil" takes 44 per cent, of this to be COg, and 

 assumes the specific gravity of the rock to be 2 '6. 



On these data, and taking the fuss as = 0-3 metre (as stated 

 elsewhere by Pfaff), the COo would exert a pressure, not of 356 

 atmospheres, but of 33*2, approximately. It appears, in fact, 

 as if Pfaff's result was, through some oversight, calculated as 

 just ten times too great. 



Perhaps there is some other explanation of the discrepancy. 

 But, lest it prove an error, I have thought well that attention 

 should be drawn to it, the statement being made on such high 

 authority. J. JoLY. 



Physical Laboratory, Trinity College, Dublin. 



