398 



NATURE 



{Sept. 17, 1874 



unspent cannon-ball impeded by a bank of earth, keeps 

 spinning and grinding in its bed for four months, and 

 then suddenly goes off with unabated velocity as if it 

 were merely ricochetting from its point of interruption ?" 

 Did the writer never hear that the motion of this 

 comet was in strict accordance with the laws of gravi- 

 tation, and Laplace used it for corrrecting the value of 

 Jupiter's mass? In these cases, and in many others, the 

 author has gone sadly astray. The accounts of the appear- 

 ance of the different comets are good and clear and are 

 well worth reading, but one or two drawings of comets 

 would have improved matters considerably. There is a 

 plate nt the beginning of the book, of the earth in a 

 comet's tail, which draws somewhat on the imagination. 

 A want of soundness with reference to mechanical laws 

 appears throughout the book, for we read of the two 

 parts of Uiela's Comet having less mass to be acted upon 

 by solar attraction than they had before separation, so 

 that the original orbit must have been altered ; and we 

 heir of a comet altering capriciously its centre of gravity 

 with reference to solar attraction. The words orbit;/al 

 and phosphortius occur frequently, we hope for the last 

 time. The book is spoilt by the endeavour to explain 

 the appearances of comets without regard to the most 

 fundamental physical laws which have so far been found 

 to be rigorously e.\act. G. M. S. 



LETTERS TO THE EDITOR 



[ The Editor does not hold himself itsponsible for opuiioiis expressed 

 by his correspondents. No notice is taken of anonymous 

 communications \ 



Pollen-grains in the Air 



Mr. Hubert Aiuy's letter printed in your issue of Sept. 3 

 appears, to agieat extent, to reconcile that gentleman's oOser- 

 vations with my own. My set of drawings have been made 

 entirely from pollen-yrains in the (//;]' state, and in this condition 

 (in which of course it is wafted through the air) I find the pollen 

 of plants fertilised by the wind, though belonging to the most 

 widely dissociated natural orders, to be uniformly, as far as I 

 have been able to observe, nearly or perfectly spherical, with no 

 prominences or furrows visible on magnifying about 250. A 

 very short immersion in glycerine would cause the protrusion of 

 the inline through the weak spots of the extine, and would give 

 to the grains of birch and hazel the spherically triangular appc.ir- 

 ance described by Mr. Airy, and represented in some of the plates 

 by an old German writer. Alfred W. Bennett 



Penmaenmawr, Sept. 9 



Fossils in Trap 



When examining the great exposure of trap and associated 

 Upper Silurian rocks at Cape Bon Ami, New Brunswick, I 

 unexpectedly found fossils in the trap. I was at the time 

 collecting agates and amygdals of calcite. One amygdal 

 attracted my attention as singularly regular in shape. On 

 detaching it from the rock and examining it with the magnifying 

 glass, I found it to be a coral, Favosites gothlandica. The fossil is 

 nearly circu'ar. Its greatest diameter is \-^^m., its smallest 

 diameter i/Viu., its greatest thickness is \ in. Notwithstanding 

 the rubbing by exposure on the shore, many of the cells 

 are quite distinct : the side attached to the trap is without 

 cells. I found a second specimen of a similar coial in 

 another part of the trap-rock. Of this the length is i in., the 

 width i'*ff. The exposed part is a section having the structure 

 perfect ; it ii slightly weathered. The fossil is indissolubly 

 united with the trap, its sharp septa penetrating it : the trap of 

 the specimen is very compact. 



These fossils arc derived from the associated strata of Niagara 

 limestone : Wenlock limestone age. 



The strata have been coral reefs : they are filled with corals, 

 Favosites and Cyathophylla. I collected magnificent specimens 

 of the former, also Crinoid joint, Orthis sp. ? Strophomena de- 

 pressa, Atrypa -.vlicularis, Khynchonclla sp., Athyris iiitida, 

 Orthoccras sp. ? 



The fossils are easily detached from tlie strata. 



I have no doubt that the notice of the occurrence of the fossils 

 in trap will be new to many of your readers. In all my investi- 

 gations 1 have not met with a similar occurrence. The first 

 example proves that the trap was, at least, in a plastic state when 

 the fossil dropped into it. The second proves that it was in a 

 fluid state. 



This is all very satisfactory to us, as proving that trap is a 

 true lai'a, although the Wcrnerinn might thereby infer that the 

 trap was a sedimentary rock. The section of the coral in the 

 trap is as perfect as sections of Lithoslrontion in the Lower 

 Carboniferous limestone of East Kiver Picton in our museum 

 collection. 



By what process were these fossils preserve 1 from destruction 

 m the molten trap? D. HoNEYMAN 



Halifax, Nova Scotia, Aug. 27 



[Our correspondent does not define in what sense he uses the 

 vague word "trap." Fossils, both animal and vegetable, are 

 of common occurrence in some kinds of ''trap," <■.;;. in the 

 different forms of tuff. We presume that the specimens he 

 refers to were of true basalt, or some other form of crystalline, 

 and once molten i;neous rock. If so the fact is interesting, 

 though possibly some of our readers may be able to adduce 

 similar cases. — En.] 



Curious Rainbow 



Three or four days ago I observed a phenomenon which may 

 possibly be interesting to some of your readers. I was standing 

 on a hillside, about 200 ft. above the sea, and saw a rainbow of 

 the ordinary description, very vivid and extending to the horizon 

 at both ends of the arch ; outside this was a se;ondary bow, also 

 very distinct, and inside the primary bow was a series of coloured 

 bands, to all appearance identical with the series in the primary bow 

 from the green to the violet, so placed that the green of this third 

 bow was next to the violet of the primary bow, and the violet of 

 the third bow the innermost of all. There was no appearance 

 of any superposition of colours, and the third bow was nearly as 

 bright as the primary, and the interval between them was hardly 

 appreciable. The whole series was concentric. I have not 

 observed any notice, in works on the subject, of a phenomenon 

 similar to this, or any hint that it might be expected according 

 to the geometrical or physical theories of the rainbow, and 

 therefore think the appearance may possibly be of rare occur- 

 rence. R. P. A. SWETTENHAM 



Glen Caladh, Kyles of Bute, Sept. 5 



Polarisation of the Aurora 



In answer to Mr. Procter's first question (vol. x. p. 355), I woidd 

 refer him to Nature, vol. vii., p. 201, where he will frnd an ac- 

 count of observations of the polarisation of tire zodiacal light, and 

 of the aurora, by Mr. Ranyard, who 'appears to have used a 

 double image prism and Savart, during the great aurora of Feb. 4, 

 1S72, and to have detected no polarisation. He refers also to 

 some observ.ations made upon the small aurora of Nov. 1 1, iSyr, 

 in which he could detect no polarisation. The only other 

 account of observations that I have met with are contained in 

 the report of Prof. Stephen Alexander on his expedition to 

 Labr.ador, given in Appendix 21 of the United .States Coast 

 Survey Report for i860, p. 30. He found strong polarisation 

 with a Savart's polariscope, and, what is most remarkable, 

 thought that the dark parts of the aurora gave the strongest 

 polarisation. This was at the beginning of July. He was in 

 latitude about 60°, and the observations appear to have been 

 made near midnight. But he does not state whether there was 

 twilight or traces of air polarisation at the time, nor does he give 

 the plane of polarisation. 



Cheltenham J. A. Fleming 



FRANCIS EDMUND ANSTIE, M.D., F.R.C.F. 



ON .Saturday, 12th inst, in his forty-first year, p"" 

 illness of only four days' duration, die' -''■?5 ^ 

 Anstie, from the consequences of a dissc'' ■* ^''' ^'' . ■ 

 flicted while he was investigating the ,iion-wound in- 



and somewhat mysterious dise?' • causes of a serious 

 time prevailed in a large sch^ -e which had for some 

 rapidly carried off sever?' -ol nt Wandsworth, and had 

 ^ of the pupils. Thus he must 



