Sept. 26, 1872J 



NATURE 



431 



fir cones and extracting the seeds. His observations on 

 the habits of the water-ouzel, its procedure under water, 

 and the food it seeks there, quite redeem that lively little 

 bird from the imputation of beini^ a destroyer of salmon- 

 spawn, and pro\e him to be the . salmon fisher's best 

 friend. But, indeed, the charms of Mr. Knox's book are 

 many, and will be deemed an acquisition by all who take 

 an interest in British zoology ; to those who are both 

 fishers and naturalists it will afford a rich treat. The tail- 

 piece to the book is a beautiful woodcut of a salmon, 

 having underneath the punning legend, "/« spc vivo." 



Physical Geography. By Sydney B. J. Skertchley, 

 F.G.S., H.M. Geological Survey. (London : Thomas 

 Murby.) 

 This is one of '• Murby's Series of Science Manuals" in- 

 tended for use in schools. It seems on the whole 

 creditably done, the information conveyed is valuable, 

 and in the main trustworthy, the author occasionally 

 drawing on his own experience for illustration. Amid 

 the many manuals on the same subject competing for 

 f.ivour this deserves to take a place, though the few illus- 

 trations introduced are wretched, and there is an occa- 

 sional attempt at fine writing. 



Rcvuc Photoi^raphiquc dcs Hopitaux dc Paris. Public 

 par Bourneville et A. de Montmdja. 4''"= Annee. 

 Avril, 1872. (Paris: Delahaye ) 

 This enterprising little publication deserves success. 

 The number before us, which, however, is only interest- 

 ing to our medical readers, contains three photographs 

 (about 4 in. by 3 in.), one of a calcified enchondroma, and 

 two of a remarkable case of encephalocele. One of 

 these e.\hibits the whole infant, the other the upper part 

 of the trunk. The details are very clearly visible, and 

 there is an account of the case by P. Budin. The Rt'viie 

 contains also a good report of recent anatomical physio- 

 logical and surgical work. 



LETTERS TO THE EDITOR 



[ The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. No notice is taken of anonymous 

 communications. ] 



The Potato Disease 



I l-EEL very much interested in the attempt you have maile to 

 connect the potato disease with cosmical phenomena, and I quite 

 ayree with you that although the Pcronospora may be the proxi- 

 mate cause, yet (or the ultimate cause we may have to look to a 

 very different set of circumstances. 



The researches of Baxendell, Meldrum, Smyth, and others, go 

 to stiow that the convection currents of the earth are influenced 

 by the state of the solar surface. Now surely anything that in- 

 fluences the motions of our atmosphere may readily lie supposed 

 to influence the distribution and activity of those disease germs 

 tliat are now believed to be present in the atmosphere. Are 

 not various kinds of blight associated with the prevalence of 

 certain winds ? 



In referring to the five great visitations of the sweating sick- 

 ness you say quite truly that we have no means of ascertaining 

 the condition of the surface of the sun during thobc years. 

 Nevertheless, indirixtlyy we may, I think, come to some sort of 

 conclusion moie or less probable regarding the sun's surface in 

 those years. 



This may, perhaps, be done by means of records of the Aurora 

 liurealis. I have not access at present to the great catalogue of 

 M. de Mairan, and I will, therefore, confine myself to the list of 

 auroral appearances given by Mr. Jeremiah in your columns for 

 November 17, 1870. Very great and extensive auroral outbursts 

 are known to occur during years of maximum sun-spots, and 

 aurorx' are phenomena which appeal too much to the imagination 

 to remain lumoticed in an unscientific age. 



If, therefore, we can tell the years of very great auroral out- 

 bursts, we can at least approximate to those of maximum sun 

 spots. 



Now (quoting from N.\TURE) "in 1574 Camden and Stow in- 

 form us that an Aurora Borealis was seen for two successive 

 nights, viz., the 14th and 15th of November, with appearances 

 similar to those observed in 17 16, and which are not commonly 

 noticed. The same phenomenon was twice seen in Brabant in 

 1575, viz. on 13th February and 2Sth September, and the cir- 

 cumstances attending it \iere described by Cornelius Gemma, 

 who compares them to spears, fortified cities, and armies fighting 

 in the air." This has every appearance of a widely extended and 

 great series of outbursts, and we may, perhaps, suppose that the 

 maximum was not far from 1575. 



Again we learn that "on September 2, 1621, the same pheno- 

 menon was seen all over France, and it was particularly described 

 by Gassendus in his ' Physics,' who gave it the name of the 

 'Aurora Borealis.' Another was seen all over Germany in 

 November 1623, and was described by Kepler." Giving equal 

 \^•e^ght to these two appearances, we may place the maximum in 

 the year 1622. 



Again we learn that " in 1707 Mr. Neve observed one of small 

 continuance in Ireland, and that in the years 1707 and 1708 this 

 sort of light had been seen no less thanylz't' times." We may in 

 this case place the maximum in the year 1 70S. 



We have thus selected as years of maximum auroral disturb- 

 ances the jears 1575, 1622, and 1708, and if they correspond 

 approximately with years of maximum sun spots, we should ex- 

 pect the distances between them to be divisible by in, which 

 Wolf as well as De La Rue, Stewart, and Loewy, agree in repre- 

 senting as the solar period. Now the difference between 1575 

 and 1622 is 47 years — a period not very different from four solar 

 periods, or 44^4 years. 



Again the difference between 1622 and 170S is 86 ye.xrs-a 

 period not very different from eight solar periods, or 88'8 years. 

 Furthermore the difference between 1575 and 170S is 133 years 

 — a period not very different from twelve solar periods, or 133 '2 

 years. 



Finally the difference between 1708 and i8i6'8, the period of 

 one of Wolf's well-ascertained spot maxima, is loS 8, which is 

 not very dilTerent from ten solar periods, or iii"o years. 



Assuming, therefore, that 1575 is not far from a period of 

 maximum sun spots, and going backwards by steps of 11 'i years, 

 we are led to the following dates: — 1552'8, I530'6, I5I9'5, 

 1508 '4, I4S6'2, as years of maximum spots, whereas the dates of 

 sweating sickness were 1551, 152S, 1517, 1506, 1485, and the 

 differences between the two sets are as follows ; i'8, 2 6, 2'5, 

 2 '4, I '2, the mean being 2't years, and the difference always m 

 the same direction. 



It is, of course, hazardous to place much confidence in these 

 results ; nevertheless, it is wortliy of remark that the greatest 

 difference between observation and calculation from hypothesis, 

 recorded in the communication, is 2 '8 years, whereas it might 

 sometimes have been 5 '6 years on the supposition that there is 

 no truth whatever in the hypothesis. 



I shall only remark in conclusion that when we have arrivel 

 at the position of being able to explain by a probable hypothesis 

 the cause of spot variations, we may perhaps be able to test our 

 conclusions by means of these early notices of the Aurora 

 Borealis. B. Stew.vkt 



Having been from home, it is only now that I have read your 

 very interesting article of .Sept. 12, on the Potato Disease. 



It is certainly most desirable that "an investigation into the 

 origin, cause, and remedies " thereof by the ablest of our scientific 

 men should be promoted ; but it appears to me that this is a cise 

 for private contributions rather than an appeal to Government. 

 I would, tlierefore, suggest that a fund be raised by subscription 

 to supply the means of offering three prizes for the above object : 

 the first I should hope would not be less than 500/ , the second 

 and third 300/. and 200/. 



These sums would offer an inducement to the ablest men to 

 devote to the object a portion of that time and talent which, with 

 many of them, forms the chief (sometimes the only) source from 

 whence their income is derived. 



The judges might be appointed by such of the subscribers as 

 could meet at a given place after due notice. 



The sum required, including expenses of advertising, &c., 

 would not be large ; there ought to be no difficulty in raising it 

 when we consider what a large interest is at stake. 



I should be happy to subscribe 5/. 



Richmond, Surrey, Sept. 23 M. Moggridge 



