NA TURE 



\_March 24, 1881 



a wing of a gigjantic dragonfly. The reverse has a small part of 

 the base, not to be seen in the obverse, with a straight sector 

 crossing the horizontal ones. The same arrangement is to be 

 seen in Isophlebia. Every other character important for nearer 

 determination is wanting in the fragment. 



Lithcntoiiiiun Harttii. — The fragment is very insufficient, and 

 recalls the venation of the Sialids, and among them those of the 

 Chauliodes type. 



Homothetus fossilis. — -This is a Sialid of the Corydalis type, 

 with a small number of transversals. The basal vein, spoken of 

 as homologous with the arculus of the Odonata, and as proving a 

 synthetic type, is the part in which the wing breaks off easily in 

 actually living species. I have not seen the type. 



Xenoneura antiquortim. — Some details given for this species 

 are not exact. It has not been observed that parts of one wing 

 cover the other ; I can only say that the wing belongs to the 

 Neuroptera, and that the venation is nearer to the Chauliodes 

 type than to any other. The famous " stridulation " apparatus 

 at the base is justly retracted by the author. 



Four new families are proposed for these insects by the author. 

 One of them, the Atoxina, is now out of the question, as Gere- 

 phemera belongs to the Odonata. The three others are only 

 indicated by extremely vague characters, in fact by no characters 

 at all. Can science accept such families ? I believe not. 



I omit Dysciitits vetusHis because this fragment is undeter- 

 minable. 



My conclusions are, that two of the insects belong to the 

 Odonata, three to the Sialids. There is no Epheraerid among 

 them, nor any synthetic species. The proofs for my statements 

 will be given in a detailed paper. H. A. Hagen 



Cambridge, Mass. 



Ice-Casts of Tracks 



As I was riding along the highway late this afternoon, my 

 attention was attracted to a phenomenon no less curious than 

 beautiful. A couple of days ago there was a fall of a few inches 

 of very damp snow, after which the temperature fell rapidly, 

 and this morning everything was frozen hard. A large dog had 

 trotted along in the snow while it was yet damp, and where it 

 lay upon the old drifts by the road-side. To-day the sun has 

 been shining very warjn, cutting away all the new snow and 

 leaving the tracks of the dog in exquisitely perfect ice-casts, thin 

 as writing-paper, and standing on the most delicate thread-like 

 columns, about an inch above the surface of the old snow. 



Lyons, N.Y., March 7 J. T. Brownell 



Migration of Birds 



The following extracts from a work entitled " Bible Customs 

 in Bible Lands," by Henry J. Van Lennep, D.D. (1875), may 

 prove interesting to some of your readers, as containing im- 

 portant and reliable evidence with regard to the migration of 

 birds, which has formed the subject of two recent letters in 

 Nature. 



Speaking of the great numbers of small birds which inhabit 

 Western Asia, as compared with Europe and North America, 

 Dr. Van Lennep explains the circumstance by the fact that 

 "even those of feeblest wing have an easy road from Ptilestine, 

 Syria, and Mesopotamia, by the Isthmus of Suez, and over the 

 narrow Red Sea, to their winter quarters in tropical Africa, 

 while nature has provided them with extraordinary means of 

 conveyance from Asia Minor southward across the Mediterranean 

 . . . The swallow, and many other birds of similar powers of 

 flight, are able to cross over the entire breadth of the IMediter- 

 ranean, especially by taking advantage of a favourable wind. 

 But many birds are quite incapable of flying over a surface of 

 350 miles from headland to headland across the Mediterranean 

 without alighting, and would require many days, and even weeks, 

 to perform the trip through Syria and Palestine. Such are the 

 ortolans, darnagas, bec-tigs, wren, titmouse, smaller thrushes 

 and finches, with a hundred other diminutive specimens of the 

 feathered tribes . . . and as the severity of the winter would 

 be fatal to them, not only in Asia Minor but even in Syria and 

 Palestine, He who is ever mindful of the smallest of His 

 creatures has provided them with means of transportation to a 

 more genial clime. Many of them, indeed, find their way 

 downward from Palestine into Arabia and Egypt, but this would 

 be difficult, if not impossible where lofty mountains and broad 

 seas intervene, and to meet such cases tlic crane has bcai pro- 

 vided. . . . Most of these birds are migratory. In the autumn 



numerous flocks may be seen coming from the north with the 

 first cold blasts from that quarter, flying low, and uttering a 

 peculiar cry as if of alarm, as they circle over the cultivated 

 plains. Little birds of every species may then be seen flying up 

 to them, while the twittering songs of those already comfortably 

 settled upon their backs may be distinctly heard. On their 

 return in the spring they fly high, apparently considering that 

 their little passengers can easily find their way down to the earth, ' 



As Dr. Van Lennep has "spent almost a lifetioae in the 

 East," I conclude he has been an eye-witness of the above facts, 

 and therefore his testimony is conclusive. G. A. 



Bath, March 16 



Sound of the Aurora 



With reference to the question mooted in last week's 

 Nature (p. 459) by M. L. Rouse as to the sounds emitted by 

 auror.'e, perhaps the accompanying extracts may be of interest, j 



Brighton, March 20 Edwd. Alloway PaukhuivST 



" He.-ord of a Girlhood," F. A. Keinhle. Vol.1. 

 _ "Standing on that balcony [at Edinburgh] late one cold clear 

 night, I saw for the first time the sky illuminated with the 

 aurora borealis. It was a magnificent display of the pheno- 

 menon, and I feel certain that my attention was firbt attracted to 

 it by the crackling sound which appeared to accompany the 

 motion of the pale flames as they streamed across the sky ; 

 indeed crackli^is; is not the word that properly describes the 

 sound I heard, which was precisely that made by i\i^ flickering 

 of blazing fire ; and as I have often since read and heard 

 discussions upon the question whether the motion of the aurora 

 is or is not accompanied by an audible sound, I can only say 

 that on this occasion it was the sound that first induced me to 

 observe the sheets of white light that were leaping up the sky. 

 At this time I knew nothing of such phenomena or the debates 

 among scientific men to which they had given rise, and can 

 therefore trust the impression made on my senses." 



I BEG to assure Mr. Rouse that about fifteen years ago, early 

 in the evening, in this very quiet locality, I listened, along with 

 my father, to the sound of an aurora, pulsing above us, across 

 the zenith, and appearing nearer to us, or lower, than most 

 auroras I had seen. The sound was some\ihat like the rustling 

 or switching of silk, and we listened to it for some time with 

 great curiosity. The aurora was not coloured, as more imposing 

 ones have sometimes appeared, but white. It recalled to me the 

 lines of Burns in a fragment entitled "A Vision." 

 " The cauld blue north was streaming forth 

 Her lights, wi' hissing eerie din : 

 Athort the lift they start and shift, 

 Like fortune's favours tint as won." 

 Dumfriesshire, March 20 J. Shaw 



Tacitus on the Aurora 



With reference to the passage of Tacitus, "Germ." 45, quoted 

 in Nature, vol. xxiii. p. 459, I would suggest that the reading 

 equorum, proposed by some commentators, is far happier than 

 deorum. "It is believed that a sound is heard, that the forms of 

 the horses and rays from a head are seen." R. O. S. 



Heidelberg, Germany 



Aberration of Instinct 



As an instance of " Aberration of Instinct," or I should rather 

 say of instinct at fault, may be mentioned the following : — It is 

 well known, I believe, that rooks in attacking young mangold- 

 wurtzel pick out the plants to obtain the wireworm at their roots. 

 It happens that plants most infested with these insects are the 

 most flagged in the leaf. Now a neighbour whose sowing had 

 been a partial failure transplanted some young wurtzels into the 

 vacant places. These of course for a few days presented a flagged 

 appearance, and were all seized on by the rooks to the exclusion 

 of the rest. Poor disappointed creatures, what must have been 

 their chagrin at finding no wireworm as they evidently expected! 



T. H. Waller 



Waldringfield Rectory, Woodbridge, March 16 



Squirrels Crossing Water 

 A CORRESPONDENT in NATURE (vol. xxiii. p. 340) is surprised 

 to learn of the squirrel taking to the water. It is not an im 



