October i8, 1900] 



NA TURE 



599 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.^ 



Collateral Heredity Measurements in Schools. 



As a result of the appeal, made in Nature last June, for aid 

 in the measurement of pairs of brothers and sisters, I have re- 

 ceived friendly help from a number of masters and mistresses up 

 and down the country. I think I have received between 400 and 

 500 data forms properly filled in. Considerable as this assistance 

 has been, I would still beg for further aid, as I want the collec- 

 tion to reach, if possible, 1000 pairs for each fraternal relation- 

 ship. I have at the present time several head-spanners free, 

 and shall only be too glad to send one to any teacher who will 

 undertake the necessary observations on six to ten pairs of 

 brothers or sisters. As I said in my former letter, the deter- 

 mination of the intensity of hereditary resemblance is a very 

 important matter, and it can, at any rate in the case of man, 

 only be achieved by co-operative eflfort on the part of those 

 interested in science. Karl Pearson. 



University College, London, October 9. 



The White Rhinoceros on the Upper Nile. 



It may interest your readers to learn that during his recent 

 notable traverse of Africa from South to North, Major A. St. 

 Hill Gibbons shot on the Upper Nile, near Lado, a rhinoceros 

 which he considered to be the white or square-mouthed rhino- 

 ceros {R. simus), hitherto only known from south of the Zambesi, 

 and now, unhappily, nearly extinct there. His determination is 

 fully borne out by the skull, which I have had the pleasure of 

 examining, and which shows all the many characters that dis- 

 tinguish N. simus from the common species. A', bicornis. 



That a rhinoceros of this group existed in Central Africa has 

 been suspected before. Dr. Gregory in " The Great Rift 

 Valley." mentions having seen in Leikipia, but failed to shoot, 

 three specimens which he believed to be R. simus. Some years 

 earlier Count Teleki shot a " White Rhinoceros" in the same 

 district, but his account has more reference to the colour than 

 to the specific determination of the animal, and his specimen 

 may only have been a pale-coloured R. bicornis. 



Now, however, Major Gibbons has fortunately set the matter 

 at rest, as there can be no question that his animal is not R. 

 ■bicornis, but belongs to the rarer southern form, hitherto 

 supposed to be practically extinct. 



The discovery of this animal in the Nile watershed brings it 

 geographically nearer to its European and Siberian ally, the 

 Pleistocene R. antiquitatis, both species being in turn, no doubt, 

 offshoots of the Pliocene R. platyrhinus of the Siwaliks. 



Natural History Museum, Oldfield Thomas. 



October 12. 



P.S. — This find has an interesting parallel in Mr. W. Penrice's 

 -discovery in Angola of a zebra allied to the true Cape Zebra 

 ■{Equus zebra), now also nearly extinct there. But in that case 

 the species proves different by its shorter hair, and much broader 

 white striping, and has been named Equus penricei. 



Disease of Birch Trees in Epping Forest and Elsewhere. 



Ix Epping Forest, and in other districts around London, 

 birch trees have been attacked during the late summer by a 

 disease which causes them to die very rapidly. In a portion of 

 the Forest known as Lord's Bushes, thirteen diseased and twenty- 

 four completely dead trees were noted on June IQ within an 

 area of about one and half acres. 



A few were attacked in the Forest in the summer of 1899, 

 but it was not till this year that the disease appeared in such a 

 destructive form. On Chiselhurst Common, Hayes Common 

 and Keston Common no signs of the disease were evident in the 

 early summer, but now dead or diseased trees may be found in 

 great numbers. Trees attacked in a similar manner occur at 

 Walton-on-Thames, by the canal between Weybridge and 

 Woking, at Lewisham and at Westerham. 



The disease is probably due to a micro fungus, Melanconis 

 stilbostoina, Tul. , for it appears on the branches of both living 

 and dead trees. The diagnosis of the disease is almost precisely 

 that of Valsa oxystoma, described as the destroyer of Alnus 

 viridis in some parts of the Tyrol. 



NO. 16 1 6, VOL. 62 1 



It would be interesting to know if any of your readers have 

 observed the disease in the Midlands or in the north of England. 



RoBT. Paulson. 

 10, Denholme Road, Maida Hill, October 8. 



Sunspots and Frost. 



In the study of winter cold, we find, I think, some striking 

 contrasts associated with different parts of the .sunspot-curve. 

 These contrasts, whether they are really due to sunspot varia- 

 tions or no, seem worthy of attention as a practical matter, 

 and an occasion for observing whether such relations are main- 

 tained in future. 



Taking the Greenwich records since 1 841, let us see how 

 many frost days there were in each three-year group following 

 the sunspot maxima 1848, i860, 1870, 1883 and 1893 ; and how 

 those sums are related to the average (which is 164 in three 

 years). The following table shows this : — 



689 



131 



Thus, each of those three-ypar groups was mild, in respect 

 of frost days, and there was a total deficiency of 131 days. 



Now, let us do the same with the three-year groups following 

 the minima, 1843, 1856, 1867, 1878, 1889: — 



927 +107 +238 



In this case, each three-year group is over average, and the 

 total excess is 107 days. The added column {b-a) shows that 

 the three-year groups after minima had altogether 2'?8 frost days 

 more than the groups after maxima, giving an average of 47 "6 

 for each pair of groups compared. 



If we group together the fourth, fifth, sixth and seventh years 

 after maxima {i.e. '52-55, '64-67, '74-77 and '87-90), and 

 count the frost days in those four-year groups, we find that the 

 latter share the character of the three-year groups after 

 minima, each having an excess of frost days over the (four-year) 

 average. We are now in the last year of another of these 

 groups (viz. 1897-1900). 



Analysing those mild three-year groups after maxima, we find 

 out of a total of fifteen years only four with more than the 

 average of frost days, and only one group (1884-86) in which 

 two of the three years had an excess. 



It occurred to me to examine what kind of summers we had 

 in those mild groups, and the following curious table was 

 arrived at : — 



M.T. Relation to 



Summers. average. 



av. 



- -8 

 + '5 

 av. 

 + -4 



Thus, the divergence from the average never gets beyond a 

 decimal value. Analysing, one finds only three of those fifteen 

 summers in which the divergence gets beyond a decimal value 

 (viz. - 2'4, - I'l and + I '4). The summers of three-year groups 

 after minima might be shown to have a distinctly opposite 

 character. But I do not lay stress on this. 



Alex. B. MacDowall. 



Simple Experiments on Phosphorescence. 



In consequence of reading your note in Nature of Septem- 

 ber 27, on M. Gustave le Bon's paper on various forms of phos- 

 phorescence, the following experiments were tried. A surface, 

 previously dark, of the sulphide of calcium, was exposed to the 



