2;6 



K/l TUKE 



[July 14, 1 88 J 



cism of a manual like this would proceed from one who 

 had actually tested its use. Improvements will gradually 

 suo-ffest themselves ; a few friendly suggestions might be 

 even ventured upon offhand. Cm p. 63, for example, 

 the following definition is open to objection: — " Trichomc, 

 a generic term for all organs developed by emergeace 

 from single cells of the epidermis." The chapter on 

 Floral Diagrams is good. But it never seems to have 

 been suggested that a genu-ne interest might be given to 

 lessons in botany by making the pupils arrange the 

 actual parts of the flovrer so as to form the diagram. 

 All that is wanted is a flat square of cork covered with 

 paper, on which four concentric circles are traced. It 

 would be best to have three such squares for each pupil, 

 with three, four, or five radiating lines drawn intersecting 

 the circles, according as flowers with a ternary, quater- 

 nary, or quinary symmetry are to be examined. As each 

 successive whorl of floral organs is removed, its parts 

 should be pinned out in their proper relative positions by 

 the pupil. The cyclical symmetry of the flower is clearly 

 brought out in this way, even where it is apparently dis- 

 guised. Some details in working the method would need 

 a little elaboration, as, for example, the treatment of 

 gamopetalous flowers ; but this may be left to the 

 ingenuity of teachers like Mr. Bettany. 

 Rabeiihorsfs Kryptogavtcn-Flora von Deiiischland, Oester- 

 reich und der Schweiz. Erster B and : i und 2 Lief. 

 Pilze, von Dr. G. Winter. (Leipzig, 1881.) 

 Few men have done their fellow-workers in science 

 greater service, even if of a somewhat unobtrusive sort, 

 than Dr. Ludwig Rabenhorst, whose recent death we 

 announced with regret (N.-iTURE, vol. xxiv. p. 108). 

 . His "Flora Algarum aqua; dulcis et submarinK" is an 

 indispensable guide to an immense labyrinth of species 

 and genera which lie scattered up and down botanical 

 literature. These are digested into a methodical enu- 

 meration which makes little attempt to be critical, but is 

 content to bring the materials together just as every one 

 who intends to study what has been done in any special 

 group without such an aid must do for himself. Had 

 Rabenhorst attempted more he would never have done the 

 useful work that he did. One very convenient feature 

 of his books is the brief synopsis of the genera of each 

 group, accompanietl by outline woodcuts of some leading 

 types. Amongst organisms whose real affinities are often 

 so obscure as the lower cryptogams, the utility of this 

 plan cannot be sufficiently approved. The woodcuts 

 often convey information at a glance which hours of study 

 and comparison would not extract from the descriptions. 

 The present work, of which two parts have so far 

 appeared, is substantially a new edition of the author's 

 " Deutschland's Kryptogamen-Flora," of which the first 

 appeared as far back aslS-14. The death of the original 

 author may, it is to be hoped, have no effect on impeding 

 its completion, as different groups are assigned to difl'erent 

 hands. Dr. Winter commencing the fungi in the two parts 

 before us. The scope of the whole work will be very 

 much enlarged, but the same convenient features will be 

 perpetuated. A speedy completion will be devoutly 

 desired by all students of European Thallophytes. 



LETTERS TO THE EDITOR 



[ The Editor docs not hold Jiimself responsible f of opinions expressed 

 by /lis correspondents. Neither can he tmdertake to return, 

 or to correspond with the '<oriters of, rejected manusiripts. 

 No notice is taken of anonymous communications. 



[ Tlie Editor urgently requests correspondents to keep their letters 



as short as possible. The pressure on his space is so great 



that it is impossible otherwise to ensure the appearance even 



oj communications containing interesting and ncrel facts.] 



The Comet 



Further measures have been obtained at Greenwich of the 



po--ition of the least refrangiile edge for three of the four cimet- 



bands with the following remits : — 



Blue band. 



4733'9±i"i 



4736-0 



6 



Yelbw band. Green band. 



Comet 563o-4±r6 ... 5i627±0'4 



I!unsen Flame S633'o ... 5i64'o 



No. of Obs. 7 ... 26 



The identity of the comet-bands with those in the first 

 spectrum of carbon appears to be clearly eatablished, but in each 

 case the comet-band is slightly shifted towards the blue. The 

 displacetuent of the green band, if real, wouM indicate an 

 approach of 47 i 14 mile-; per second, whereas the comet wa^ 

 actually receding from the eartli at the rate of about twenty 

 miles per second. Such a displacement might, of course, be 

 explained by an emission of cometary matter on the side towards 

 the earth, but it would seem more probable that it is due 

 to the circumstance that the edge of the comet-band is not 

 quite sharp, and that a small pirtion on the red side is 

 cut off. This would apply with still more force to the yellow 

 and blue bands, which indicate somewhat larger displacements 

 towards the blue. The disjilacements however, though all in 

 the same direction, are not largely in excess of the probable 

 errors. The comet-bands were compared with those given by 

 vacuum-tubes containing cyanogen and marsh-gas, as well as 

 with those of the Bunsen-burner flame, and three forms of 

 spectroscope were used, viz. (l) the half-prism spectroscope with 

 a dispersion of lSh° from A to H, and a magnifying power of 

 14 ; (2) the half-prism spectroscope reversed (as fjr prominence 

 observations), giving a dispersion of 5° from A to H and great 

 purity of spectrum, with a magnifying power of 28 ; and (3) the 

 star spectroscope with a si. gle prism of flint. No measures were 

 obt.iined of the band in the violet, which was only seen on 

 two occasions. It appeared to be sensibly coincident with 

 the band in the first spectrum of carbon at 431 1. 



Mr. Maunder also noted several of the Fraunhofer lines in 



the continuous spectrum, in particular F (the position of which 



was determined by comparison with H/3) and two other lines 



w hich were respectively near E and a strong doulile line at 5327. 



W. H. M. Christie 



Royal Observatory, Greenwich, July 12 



I SUCCEEDED in photographing the comet in Auriga on Friday 

 night, June 24. Since then I have taken several photographs 

 of it. One made la't night with an expomre of 2 hours 42 

 minutes shov\s the tail about lo° long. There are many stars 

 on the plate, some shining through the tail. 



Henry Draper 



The Physiology of Mind Reading 



I HAVE received from Dr. G. M. Beard of New York (well 

 known for hi^ studies of Trance and related states) a letter in 

 reference to the experiments with Mr. Bishop, of which Mr. 

 Romanes has given an account in NATURE. Dr. Beard, writing 

 before our experiments were carried out, mentions his own 

 investigation, years ago, of much more remarkable performances 

 than Mr. Bishop's, and incloses an article "On the Physiology 

 of Mind-Reading," which he contributed to the Popular Science 

 Monthly (New York) as far back as February, 1877. If ''"* 

 article had been shorter I would fain hive asked you to reprint 

 it, giving as it does a far more varied record of facts than came 

 under our observation, and a series of caret uUy-drawn'conclusions 

 within which our conclusion falls. I will only say that if I had 

 known of this article I shoul 1 hardly have thought it worth while 

 to spend time in the trial of Mr. Bishop's powers, or even had 

 the curiosity to attend that firil meeting amid the cloud of scien- 

 tific witnesses. G. Croom Robertson 



July 9 



Mind and Muscle-Reading 

 Kindly allow me to correct a printer's error in my letter of 

 last week. In describing the case of so-called thought-reading 

 examined by myself in the clergyman's family in Derbyshire, 1 

 wrote: "The failures in my examination did not amount to 

 one in ten, and were a smaller fraction when the children were 

 not embarrassed by strangers," &c. The word "my" was 

 printed "any," thus destroying the meaning of the sentence. I 

 will just add that the clergyman in question is an old graduate of 

 Trinity College, Dnblin ; his integrity is above suspicion, and 

 even did not his position as a Christian minister negative the 

 idea of trickery, the last experiment which I described disposes 

 of this very natural explanation. W. F. Barrett 



