January 12, 1905] 



NA TURE 



245 



the preparation of the EngUsh ephemeris, and perhaps 

 are so still. Bessel gave a more thoroughly con- 

 secutive discussion, which Chauvenet followed in his 

 treatise, and this last forms the basis of Mr. 

 Buchanan's work. The practical part of the arrange- 

 ment does not seem to be easily systematised. A 

 computer finds some difficulty in translating the 

 formulje into numbers. There are to the uninitiated 

 continual ambiguities about the quadrants; and the 

 manner in which angles are to be reckoned is fre- 

 quently a stumbling block to the unwary. Perhaps 

 these little difficulties are more noticeable in Wool- 

 house's method than in Bessel's, but it is with the view 

 of limiting these troubles and of giving a convenient 

 arrangement to the whole of the work ' that Mr. 

 Buchanan has written his book. In his time he must 

 have met with all the difficulties with which a young 

 computer has to contend, and must have removed these 

 out of the path of many. Knowing these pitfalls, he 

 has done his best to get rid of them by suitable explan- 

 ations, and probably with success. But those who 

 have conducted pupils through carefully worked 

 examples know only too well that a fresh set of diffi- 

 culties is apt to reappear with a new case. 



The author has divided his book into two parts. 

 In the first he treats of solar eclipses and the method 

 of deriving the various curves which are necessary for 

 (he exhibition of the whole circumstances of the 

 phenomenon on a map. Here we get the north and 

 south limits of total and partial eclipses, the position 

 where the eclipse begins and ends with the sun in the 

 horizon, and one can follow the method by which 

 are drawn those weird curves on the eclipse maps that 

 accompany every nautical ephemeris. By way of 

 adding a little lightness to a rather dreary subject, we 

 may notice some curiosities the explanation of which 

 is not very readily seen without the assistance of a 

 competent guide, such as the occurrence of a north 

 limiting curve of totality falling south of the south 

 limiting curve. Ingenuity might construct some 

 further troublesome problems of this nature when the 

 clue is furnished, and one can imagine an examiner 

 exulting over the discovery of such oddities, affording 

 as they do opportunity for worrying unhappy candi- 

 dates who fall into his hands. 



In the second part of the book we have detailed 

 the method of computing the circumstances of lunar 

 eclipses, occultations of stars by the moon, and of the 

 transits of Venus and Mercury. These are practically 

 particular cases of the same problem as that treated 

 in the first part, simplified by certain conditions. In 

 the case of the lunar eclipse, the absolute position of 

 the moon and shadow are independent of the position of 

 the observer on the earth, and therefore the effects of 

 parallax can be treated much more simply. We 

 notice that the semi-diameter of the shadow is in- 

 creased by the fiftieth part of its amount, in preference 

 to the older estimate of 1/60, but the whole question 

 of semi-diameters is a troublesome one, which will 

 soon have to be treated with great rigour. The 

 occultation semi-diameter is not altogether satis- 

 factory, and some international convention is needed 

 to secure uniformity. From a letter from Dr. 

 NO. 1837, VOL. 71] 



Downing, quoted by the author, we gather that the 

 occultation diameter of the moon, as used in the pre- 

 paration of the English " Nautical Almanac," differs 

 2".36 from that employed in eclipse calculations. But 

 we find a little difficulty in following the author in 

 his reference to authorities. In the matter of lunar 

 parallax, Adams is not quoted, and Lardner's " Hand- 

 book of Astronomy," or Proctor on "The Moon," 

 can scarcely be considered original and trustworthy 

 sources. W. E. P. 



ENGLISH FIELD-BOTANY. 

 Flora of Hampshire, including the Isle of Wight. By 

 Frederick Townsend, M.A., F.L.S. Second edition. 

 Pp. xxxviii 4-658. (London : Lovell Reeve and Co., 

 Ltd., 1904.) Price 21s. net. 



ENGLISH field botanists frequently complain that 

 the British flora has not yet received the careful 

 critical attention which has been lavished on Con- 

 tinental floras. To a certain extent this is doubtless 

 true. We have no manual that for thoroughness of 

 treatment and wealth of reference to original descrip- 

 tions and type-specimens can compare with Rouy and 

 Foucault's " Flore de France "; at the same time there 

 is an abundance of valuable information scattered 

 through our numerous natural history journals only 

 waiting for some energetic and widely experienced 

 systematist to collate and bring together in a really 

 satisfactory British flora. There are several botanists 

 eminently fitted for such an undertaking, and it is 

 urgently to be desired that one or more of them should 

 take the matter in hand. Meanwhile, our numerous 

 and rapidly accumulating county floras are paving the 

 way to a complete botanical survey of the British 

 Isles. 



In Mr. Townsend 's " Flora of Hampshire and the 

 Isle of Wight " we have one of the best books of its 

 class, and the work and careful attention expended 

 upon its production must have been very considerable. 

 The volume opens with a chapter on topography and 

 climate. This is followed by an account of the geo- 

 logical structure of the district, including a summary 

 of Mr. Clement Reid's researches on the fossil seeds 

 of the .Stone and Silchester beds of the newer Tertiary 

 formation. In his list it is particularly interesting to 

 notice the names of several plants usually regarded 

 as weeds of cultivation, or as colonists, such as 

 Brassica alba, Boiss., Thlaspi arvense, L. , Linuni 

 iisitatissimum, Linn., and also damson and plum. 



The now generally approved method of dividing a 

 district into botanical areas according to its river- 

 systems is here in the main followed, and a useful map 

 of the county is appended. Turning to the systematic 

 section — by far the larger portion of the book — so 

 many points call for attention that it is quite impossible 

 within the limits of a short notice to mention more 

 than a few of them. In the section devoted to 

 Ranunculus, what appears to be a satisfactory 

 account of the forms of R. acris is given; this will be 

 appreciated by many collectors. The name Nymphaea 

 alba, Linn., is retained instead of Castalia speciosa. 



