572 



NATURE 



April 17, 1884 



Elemcnic dcr Orgaiwgraphic, Sys/ciiia/ik, ttnd Biologic 



der P/?a>i~i'ii. ' Von Dr. Julius Wiesner. (Wien : 



Alfred Holder, 1884.) 

 This is the second volume of a more extensive work 

 entitled " Elemente der wissenschaftlichen Botanik," the 

 first volume of which deali with the anatomy and physio- 

 logy of plants. The first part of this the second volume 

 is occupied with organography : the author recognises 

 five fundamental types of vegetative organs, viz. " phyl- 

 lom, caulom, rhizicom, trichom, thallom," and thus ig- 

 nores the conclusion of Sachs, that stem, leaf, and root 

 are not coordinate categories, but that the root should 

 rather be coordinated with the shoot, a structure com- 

 posed jointly of stem and leaf. Further, he ciles the 

 sporangia of Ferns as exauiples of trichomes (p. 5), and 

 thus does not adopt the view of Goebel, that the 

 sporangium is an independent organ, and is not refe-rable 

 to the categories of vegetative organs. These two points 

 are sufficient to show that the book is not abreast of cur- 

 rent morphological opinion. 



The second part is devoted to the systematic study of 

 plants. The arrangement adopted is that 06 Eichler's 

 ".Syllabus," in which the classification of Angiosperms is 

 different from that in current use in England. This 

 section appears to consist chiefly of an enumeration of 

 facts, and the student is left to draw his own comparisons 

 between the plants described. 



Then follows a part on " Biology," a very readable 

 treatise on the life of the individual, reproduction, and 

 the origin of species. As an appendix a short history of 

 the development of botany is given, and in a few pages of 

 notes, references are given to the most important works 

 on various branches of the subject. It is surprising under 

 the head of classification of Phanerogams (p. 424) to find 

 no mention of the " Genera Plantarum" of Bentham and 

 Hooker, the most important publication of the sort in 

 recent years. The book is illustrated by numerous wood- 

 cuts, many of which are taken from older books, for 

 example Schleiden's " Grundziige." Looking at the book 

 as a whole, there is nothing sufficiently new either in the 

 material or in the treatment to recommend it above others 

 already before the public. 



been introduced, and the use of breechloaders instead of muzzle 

 loaders has allowed the use of better means of giving rotation. 



Of course the present coefficients still hold good for compara- 

 tively short ranges, and for heavy projectiles, because then the 



loss of velocity is little on account of the small — . But when 



the 



LETTERS TO THE EDITOR 



[ The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communications. 



[The 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 insure the appearance ez-en 

 of communications containing interesting and novel facts,'] 



On the Motion of Projectiles 



I HAVE read with great interest Mr. Bashforth's article on 

 a new method of estimating the steadiness of elongated shot 

 when fired from large guns, and I have no doubt that we should 

 have a much better knowledge of every new gun to be brought 

 into service if we could try it, using the Bashforth chronograph, 

 which is the most perfect for measuring the times occupied by a 

 sjiot in passing over a succession of equal distances. That would 

 give us at once the coefficient of resistance of the air to the projec- 

 tiles used in that special gun, and then by very simple formula: 

 and tables the calculation of trajectories (which is one of the 

 main points in artillery) would be a very easy task. 



Instead, with the present system, viz. knowing only the muzzle 

 velocity, we must rely for these calculations on the coefficients 

 •letermined with only one sort of projectiles ; and of course such 

 cf>efficients must vary very much (more, perhaps, than is gene- 

 rally thought) with different projectiles, with different shapes 

 iif the head, and especially with the different methods of giving 

 rotation. 



Lately many improvements have been made in the form of 

 tlie projectiles ; many ogival-headed shots of two diameters have 



ri" 



is rather large, as in the case of small guns or rifles. 



then the coefficients Kr. arc less reliable. 



I have had great experience in calculating with the Bashforth 

 method, and I have been able to calculate trajectories for heavy 

 guns, which were not far out from the actual practice ; I had 

 still better results using Prof. Niven's method and table ; but 

 when I had to calculate trajectories for small guns, both these 

 methods failed to give me reliable results. 



For instance, in calculating the trajectories for the Nordenfeldt 

 one-inch gun, I had with Bashforth's method for an angle of 

 elevation of 9° a range of 2282 yards, and for 12° of elevation a 

 range of 2539 yards : instead by actual practice the elevations 

 required were found to be — 



For 2200 yards ... ... ... ... 7° 12' 



,, 2400 ,, ... ... ... ... 8° 20' 



,, 2600 ,, ... ... ... ... 9" 36' 



The bullets have an ogival head struck with a radius of one 

 diameter and a half, therefore they are not different in shape 

 from the shots used by Mr. Bashforth in his experiments. 

 Besides I divided the trajectory into many small arcs, and I was 

 very careful in applying the correction for the different density 



of the air, viz. using always the formula — ( I ± iKi,, in- 



^ w V 534"22/ 



stead of simply - K,,. I was even rather afraid of overdoing 



7V 



this correction, taking a lighter weight of the air than was 

 necessary ; and I was very much astonished when I saw that the 

 trajectories calculated were much too short. 



It seems to me also that the correction to be applied when the 

 bullet rises to a great height, requires a little more consideration, 

 and a thorough mathematical investigation. 



I think that the jDroblem of a body moving in a medium which 

 becomes less and less resistant as the body advances through it 

 is more complicated than we would think at first, and cannot be 

 dealt with by only considering the density of the medium equal 

 to the mean of the densities at the two terminal points. 



E. RiSTORI 



Christian Conrad Sprengel 



The interest in my note on Sprengel (N'.'^ture, vol. xxix. p. 

 29) may excuse some additional facts. In the Life of Dr. E. L. 

 Heim (by G. W. Kessler, Leipzig, 1S35, 8vo) the following is 

 reprinted from Helm's diar)', vol. ii. p. 72 : — 



" I read Rector Sprengel's work with indescribable satisfac- 

 tion. Since the time when I read Hedwig's system of the fructi- 

 fication of the mosses, fourteen years ago, I never had such a 

 great and thorough pleasure as to-day. I cannot admire enough 

 the power of observation, the untiring assiduity, the acuteness, 

 and the correct and clear exposition of the facts which he had 

 observed. His work is a masterpiece, an original, which gives 

 him honour and of which Germany can be proud.'" 



Dr. Heim, who afterwards became a distinguished physician 

 in Berlin, Prussia, was an enthusiastic mycologist, who had 

 made the acquaintance of Sir J- Banks and Solander, had 

 studied carefully Dillenius's Herbarium in Oxford, had later 

 visited Gtertner and Koelreuter. He speaks rather enthusiastic- 

 ally about this naturalist, who showed and explained to him his 

 experiments. Dr. Heim gave also the first instructions in botany 

 to .•Mexander von Humboldt. 



Mr. Kessler, the editor of Heim's Life, says (vol. i. p. 2S6) : — 

 " Heim found in Rector Sprengel, to whom he gave the first 

 instructions iji botany, a remarkable student. Sprengel repaid 

 largely all pains which Heim had spent on him by the fruit of 

 his careful studies." 



The editor wrote this in 1835, and the fact that he selected out 

 of the diary the above-quoted note proves well how much 

 Sprengel's work was appreciated and admired even by non- 

 scientists. 



In Koenigsberg, Prussia, Prof. C. F. Burdach, in his yearly 

 lectures on physiology, taught and appreciated highly Sprengel's 

 discoveries. In his large " Physiolog)-, " published in 1826 with 



