June lo, 1880] 



NATURE 



119 



wanting either in remarkable forms ; thus E. alpina is 

 found only on the summit of Mount William, Victoria, at 

 an elevation of over 4,000 feet, and its area is limited to 

 the top of this one peak, for it does not even extend to 

 any of the other summits of the chain of which Mount 

 William is the culminating point. This species has been 

 cultivated in the Melbourne Gardens from seeds col- 

 lected in 1853, but even in good soil it retains a dwarf 

 bushy habit, having in a quarter of a century not grown 

 over a dozen feet in height, and showing little tendency 

 to form a distinct stem. This species offers, perhaps, 

 the most remarkable example of limited geographical 

 distribution in the group. The Honey-scented Eucalypt 

 (E. tnelliodord) is what is called, among such giants, a 

 middle-sized tree, exceptionally attaining a height of 

 some 200 feet'; it will live on poor soil. In an official 

 report presented in 1869 to the Victorian Parliament, Dr. 

 Mueller pointed out that one ton weight of its branches 

 and leaves, if gathered fresh, would yield about 2 lb. 

 12 oz. of pure potash, and a much larger quantity of 

 crude pearl-ash. Another spscies, known from its odour 

 as the " peppermint tree " l^E. ocionita), would seem to 

 be a great favourite with a destructive nocturnal cock- 

 chafer. Through the immense clearings effected for 

 agricultural settlements, the number of insect-eating birds 

 has greatly diminished, and the increase of this species 

 of Melolontha is not properly kept in check. They prey 

 on the foliage of this Eucalypt, and Mr. Otto Tepper, 

 writing in the Transactions of the Philosophical Society 

 of Adelaide (February, 1878), states that it is being 

 extensively destroyed from this fact. 



The plates accompanying the descriptio ns of the species 

 published in these decades give ample details of the 

 leaves, flowers, and fruits of the species ; they appear, so 

 far as the stems with inflorescences are concerned, to be 

 perhaps a little too stiff and formal. Sometimes details of 

 thepecuhar wood structures are added, and on one special 

 plate transverse sections of the anthers'of some fifty-eight 

 species are figured. The London agents for this work 

 are Messrs. Triibner and Co. 



OUR BOOK SHELF 

 A Short Geography of the British Islands. P)y John 

 Richard Green, M.A., LL.D., and Alice Stopford 

 Green. (London : Macmillan and Co., 1879.) 

 "Geography, as its name implies, is an 'earth-pictur- 

 ing,' a presentment of earth, or a portion of earth's 

 surface in its actual form, and an indication of the 

 influences which that form has exerted on human history 

 or human society. To give such a picture as this of. our 

 own country, m however short and simple a fashion, is 

 the aim of the present work." Mr. and Mrs. Green have 

 carried out the task they have here indicated in a masterly 

 manner. The method they have adopted is the only 

 scientific method on which a text-book of geography 

 of this class can be constructed. Mr. Green, in his 

 preface, speaks with just horror of the majority of text- 

 books, with their dreary array of tables and " facts " and 

 figures, which makes what ought to be one of the most 

 interesting of lessons a burdensome and unprofitable 

 penance. 



In the first seven chapters the authors give a clear, 

 instructive, and completely interesting sketch of the great 

 physical features of our islands, and of their relation to the 

 continent of Europe. The mouatain groups, the uplands, 

 the plains, and the rivers are brought before the student in 



their natural or scientific aspect, with just such details 

 easily worked in as will give a clear picture of the various 

 features. The counties are then grouped in their natural 

 order, and each is treated after the same method as that 

 followed in the general sketch. The great physical features 

 are brought out first of all, the regions of the chief natural 

 resources of the country indicated, and thus the mind of 

 the pupil is prepared to understand how the political, 

 social, and industrial features have come to be developed 

 as we find them at the present day. "Facts" enough to 

 satisfy any humane examiner are given, and the principal 

 data and figures are collected in a few well-arranged 

 tables. Great care has evidently been taken to obtain 

 accurate and recent information both with regard to 

 physical geography and topographical, industrial, and 

 other statistics. Besides four coloured maps, there are 

 twenty-four special sectional maps appropriately intro- 

 duced throughout the book, which must prove of great 

 use in impressing the facts upon the mind of the learner. 

 We trust the Geography will be largely introduced into 

 our schools; we are sure that the scholar at least would 

 welcome it. Its style and method, moreover, render it 

 attractive and instructive reading to those who have 

 long left the school of their childhood behind. 



LETTERS TO THE EDITOR 



[ The Editor does not hold Jiimself responsible fir opinions expressed 

 by his correspondaits. Neither can he undertake to return, er 

 to correspond with the writers of, rejected manuscripts. No 

 notice is talien of anonymous coiniiiunications. 



[The Editor urgently requests correspondents to keep their letters as 

 sliort as possible. The pressure on his space is so great that it 

 is impossible cthei~wise to ensure tiie appearance men of com- 

 munications containing interesting and novel factsi\ 



The Visibility of Mercury to the Naked Eye 

 In Nature, vol. xxi. p. 474, 1 find the following : "Mercury 

 was seen at Paris on May (meant for March) 10 and 11 with the 

 naked eye, owing to the transparency of the atmosphere and the 

 great elongation of the planet. . . . The observation was made 

 by MM. Henry brothers at the Paris Observatory." 



Must net " the transparency of the atmosphere" have more to 

 do with the visibility of this planet than is usually supposed ? 

 The leading circumstances affecting the question, the amount of 

 the planet's elongation, the inclination of the ecliptic in which it 

 is situated to the horizon, heliocentric latitude, (Szc, being of 

 course the same at each apparition in England, on the Continent, 

 and in North America, how shall we otherwise account for some 

 of the facts of the case? The remark is current respecting 

 Copernicus that he never obtained a view of Mercury. And 

 perhaps the general impression as to its visibility — that it can be 

 seen only at the most favourable junctures, and for but a few- 

 days at a' time— is reflected in the quotation above. 



As a contribution to the question as it may be affected by the 

 variable element of climate, atmosphere, I tabulate herewith the 

 results of several years' careful though not thoroughly systematic 

 observation of the planet at this geographical position, latitude 

 44° 53' N., longitude 93° 05' W., elevation 800 feet above sea- 

 level ; — 



Time observed. 



Days. G. Elong. 



Date. 



1877 ... April 29 to May n ... 13 ... 21 5 ... May 3 



1578 ... Sept.-Oct. ... — ... 17 S3 ••• Sept. 26 



1579 ••• Ian. 7 to Jan. 29 ... 22 ... 2403 ... Jan. 16 

 18S0 ... Feb. 29 to March 19 ... 20 ... iS 22 ... Marchio 



It will be observed from the table that I followed Mercury 

 with the naked eye at its last appearance in the west (when it 

 was seen in Paris), from February 29 to March 19. I had 

 intended to look for it a day sooner, February 28, as a crucial 

 test as to how early it could be seen at that apparition, for it 

 came into conjunction with Jupiter that day and would be 

 approximately pointed out by the latter planet. But the state 

 of the sky would not permit. Looking for Jupiter the next 

 evening, so as to take bearings from him, I saw Mercury fir»t, 

 over a degree to the north-east of wliere Jupiter was when found. 

 So I am confident that Mercury was within reach of the naked 



