5IO 



NA TURE 



lApkil 2, 1908 



find out whether his results with 7 rays hold also for 

 X-rays. 



Kolluwing closely Prof. Bragg's method of piocedurc 

 with pairs of metals consisting of lead and aluminium, 

 copper and aluminium, and copper and lead, I found that 

 in every case the ionisation due to the " emergence " 

 secondary kathode rays was greater than that due to the 

 " incidence " rays. The " incidence " secondary rays were, 

 in different experiments, from 50 per cent, to 90 per cent, 

 of the " emergence." ft appeared, however, that the differ- 

 ence was not as large in the case of lead as in the case 

 of copper. This is in agreement with Prof. Bragg's result 

 for 7 rays. 



.\ separate experiment showed that the thickness of the 

 layer of copper from w'hich the secondary rays can emerge 

 is not great enough to absorb the primai-y rays to an extent 

 sufficient to account for the marked difference between the 

 ** emergence " and " incidence " secondary rays. 



On the other hand, however, both the " emergence " and 

 " incidence " secondary radiation produced greater ionisa- 

 tion when it came from a metal of high atomic weight 

 than when it came from a metal of lower atomic weight. 

 This difference was very marked with the above-mentioned 

 pairs, and also with lead and carbon. This is directly 

 opposite to the effect observed by Prof. Bragg with 7 rays. 



It should be noticed that the ionisation chambers used 

 in these experiments were so short that a very small frac- 

 tion of the secondary X-rays coming from the metals was 

 absorbed in them, while they were long enough to absorb 

 all the secondary kathode rays. Thus practically all the 

 ionisation was due to the secondary kathode rays. 



Although these experiments, together with those of Prof. 

 Bragg, show that for both X-rays and 7 rays the secondary 

 kathode rays are not produced equally in all directions, I 

 cannot agree with Prof. Bragg that the evidence is con- 

 clusive that X-rays and 7 rays must consist of some type 

 of radiation other than electromagnetic pulses. The reason 

 he gives on the neutral pair theory for lack of symmetry 

 in the secondary rays is that these secondary rays are the- 

 negative parts of the primary pairs. As these primary 

 neutral pairs possess momentum in the direction of pro- 

 pagation, it is natural to suppose that their negative parts, 

 when liberated from the positive, would be more likely 

 to continue in their original direction than to turn back. 



On the other hand, an electromagnetic pulse possesses 

 momentum also in the direction of propagation. Though 

 little is known of the mechanism of the production of 

 secondary kathode rays by ether pulses, it is not unreason- 

 able to suppose that an ether pulse could contribute some 

 of its momentum to the secondary kathode particles, 

 causing them to go more in the direction of propagation 

 of the primary than in any other. 



Since we know that X-rays, which come from a region 

 where electrons are being violently accelerated, must consist 

 in part, at least, of ether pulses, and since all the experi- 

 mental evidence previously gathered in regard to their 

 nature has been favourable to the ether pulse theory, it 

 seems to me more reasonable to look to the ether pulse 

 theory for an explanation of both X-rays and 7 rays than 

 to a theory of neutral pairs. It must, however, be recog- 

 nised that this lack of symmetry in the secondary kathode 

 rays is a difficulty in the way of the ether pulse theory 

 which needs explanation. I hope soon to determine by 

 means of absorption experiments whether this lack of 

 symmetry is due to a difference in penetrating power or 

 quantity of secondary kathode rays. 



Charlton D. Cooksey. 



Sheffield Scientific School, Yale University, New 

 Haven, Conn., March 7. 



Martinmas in May. 

 Sir Nor.max Lockver in his book on " Stonehenge " 

 connects the festival of St. Martin, which falls on 

 November 11, with the beginning of winter in the May- 

 November year, which falls astronomically on Js'ovember 9. 

 He does not, however, seem to be aw^are that there was 

 another festival of St. Martin which fell on Mav 12. This 

 was the SiibveyxMo St. Martini, a festival which was 

 appomtcd to be observed by a council held at Tours in 

 84 1 to commemorate the restoration of the relics of the 



NO. 2005, VOL. yy] 



saint to Tours after they had been hidden on account of 

 the incursions of the Northmen. Sir Harris Nicolas in his 

 " Chronology of History," published in 1838, stated that 

 the festival was still observed in the province of Tours. 

 The date of the appointment of the festival is late, but 

 reverence for sacred stones survived until long after that 

 time, and it might be worth while to try to discover 

 whether any connection can be traced between the appoint- 

 ment of the festival and an attempt to discourage the old 

 stone-worship. 



It seems clear that it was this festival of the Siibvenlio 

 which is alluded to in the entry in the Parker Manuscript 

 of the Old English Chionicle for the year 913 : — " In 

 this year about Martinmas King Edward' bade build the 

 northern fortress at Hertford, between the rivers Maran, 

 Beane, and Lea : and then after that in the summer 

 between Gang-days and Midsummer King Edward went 

 with part of his forces to Maldon in Essex." The King 

 opened his campaign at Martinmas, May 12, by commen- 

 cing a fortress at Hertford, and then between Rogation- 

 tide (May 23-25) and .Midsummer he marched to Maldon. 

 The fact that the chronicler regards the period between 

 May 25 and June 24 as summer has a bearing on the 

 question of the observance of a May-November year. It 

 is likely that the Martinmas of 919 is also the May festival, 

 but it is clear that the Martinmas of 918 and of 921 must 

 be the festival in November. C. S. Taylor. 



Banwell, March 24. 



An Annotated Copy of Newton's " Principia." 



About three months ago I was asked to look through 

 a list of old books, which had recently come to Australia 

 as portion of the personal property in an estate which had 

 been in Chancery some years. The books had become the 

 property of a resident of this city, who employed an agent 

 to dispose of them. 



Among a number of books which I bought was a copy 

 of Newton's " Principia," and when I came to examine it 

 more closely 1 .found that it was one of the original edition 

 of 1687, with the imprimatur of S. Pepys " Reg. Soc. 

 Prases Julii 5 1686." I found also that it contained 

 nearly five pages of MS. additions and corrections for a 

 second edition, written in Latin, as well as numerous 

 corrigenda throughout the book, with occasional detailed 

 alterations in the diagrams. 



Inside the cover, in another handwriting, there was the 

 following note : — " The .'Amendments in this book were 

 written by Sir Isaac's own hand. See his original MSS. 

 of his Optics in Trin. Coll. Library, Cambridge." 



I have since compared the handwriting of these " addi- 

 tions and corrections " with a facsimile of Sir Isaac 

 Newton's handwriting in the Commonwealth Parliamentary 

 library, and consider there is a distinct similarity. 



I have now had the first two pages of the notes photo- 

 graphed, and have forwarded them to the librarian of the 

 college referred to in the note, with the view of a further 

 comparison. 



The notes are punctiliously detailed, with a reference to 

 each page, and the alterations in the body o'f the text of 

 the book are made with almost microscopic care. .\s the 

 notes are headed as intended for a second edition, I cannot 

 see what other source but the mind and hand of the author 

 they could have come from. 



I am informed by the former owner of the book (Mr. 

 H. C. Elderton) that it belonged to the family of James, of 

 Ightham Court, Kent, probably to Sir Demetrius James, 

 who is supposed to have been knighted about the year 1685. 

 It and a number of other old books formed a small collec- 

 tion which were set apart, packed in oak chests, and 

 stowed away in an old clork-tower, where they remained 

 ever since until brought to .Australia. 



I shall let you know the result of my inquiries, and, in 

 the meantime, perhaps some of your numerous scientific 

 readers may be able to throw some light on the book's 

 history, for if it should be Sir Isaac Newton's personal 

 copy, and contain his personal notes, it must become an 

 object of great interest to the scientific world. 



Bruce Smith. 



149 Phillip Street, Sydney, .Australia, February 25. 



