NA TURE 



[May 3, 1900 



Similar experiments have been made with other crops, 

 as, for instance, potatoes, and the importance of such 

 experiments is, as stated further on in the book, " because 

 only such knowledge as this can show how economical 

 or how wasteful our methods of tillage may be, and 

 how nearly we are realising the largest profits which are 

 possible to the business." 



The conditions of rainfall under which irrigation is 

 practised in different parts of the world are discussed, and 

 the means of " conserving the moisture of the subsoil " by 

 proper tillage pointed out. An excellent account is given 

 of the depth of root penetration in the soil, which is illus- 

 trated, as is the rest of the book, by some very good and 

 instructive engravings. A short account is given of 

 sewage irrigation ; and the idea that the milk of cows fed 

 on sewage produce is in any way detrimental is disposed 

 of by quotations from Sir Henry Littlejohn, and from Mr. 

 Spier, the Scottish Dairy Commissioner. Methods of 

 diverting streams for irrigation are carefully described 

 and fully illustrated, as also are the methods of applying 

 the water to the ground. In Part ii. (a small portion at 

 the end of the book) the necessity for soil drainage is 

 insisted on, and the methods of carrying it out are 

 described. 



The book altogether is very readable, although the 

 spelling of some of the words seems curious to an English 

 reader. It is also well printed, and the only misprint 

 noticed is on p. 403, where the word " denitrification " is 

 used instead of "nitrification." W. H. C. 



The Refraction of the Eye, including a Complete Treatise 



on Ophthalmometry. A Clinical Text-book for Students 



and Practitioners. By A. Edward Davis, A.M., M.D. 



Pp. 431. (New York : The Macmillan Co., 1900.) 

 This volume should prove a valuable addition to the 

 library of the ophthalmic surgeon, for though several books 

 on retinoscopy have been published, this is the only work 

 on ophthalmometry yet written in English. 



It comprises a description of Javal and Schidtz's modi- 

 fication of Helmholtz's ophthalmometer, together with full 

 instructions in the use of the instrument ; the necessity 

 of forming a clear mental picture of the state of the eye 

 from the results of an experiment being rightly insisted 

 upon. 



One hundred and fifty illustrative cases are included 

 in the text, and a comprehensive index has been ap- 

 pended, so that the student can readily find a parallel to 

 any case which may give him trouble. One hundred 

 and nineteen diagrams, includmg a clear and well-drawn 

 woodcut of the ophthalmometer of Javal and Schiotz, are 

 distributed throughout the text. 



Although the advantages which may be gained by the 

 use of the ophthalmometer are insisted upon, the author 

 has taken great pains to indicate the limitations of its 

 usefulness. By its aid we may determine with accuracy 

 the radii of curvature of the cornea in various meridians ; 

 but the author endorses the generally accepted opinion 

 that there is no definite relation between the curvature 

 of the cornea and the refractive condition of the eye, as 

 far as hypermetropia or myopia are concerned. Myopia 

 usually depends upon an elongation, and hypermetropia 

 upon a shortening of the axis of vision. Strangely 

 enough, in cases of extreme myopia, a somewhat flat- 

 tened cornea is generally met with. Nevertheless, in 

 cases of simple hypermetropia and myopia, the ophthal- 

 mometer eliminates the question of corneal astigmatism. 

 The routine of examination followed by the author is (i) 

 use the ophthalmometer ; (2) use trial lenses and test 

 cards ; (3) use the ophthalmoscope ; (4) if after two tests 

 on different days the result is still unsatisfactory, employ 

 a mydriatic and use the retinoscope in addition to the 

 other tests. It is stated that (i) to (3) suffice for 99 per 

 cent, of uncomplicated cases. 



In the use of test glasses, it is recommended that a 

 NO. 1592, VOL. 62] 



series of positive lenses, gradually increasing in power, 

 should first be employed; By this means spasmodic ac- 

 commodation is avoided. The fact that the use of atropine 

 can so often be dispensed with is of great importance, 

 since many men might hesitate to have their eyes e>c- 

 amined if this necessitated a temporary cessation of their 

 business duties. 



A number of instructive cases are included, showing 

 the serious results which may follow on the prescription 

 of unsuitable glasses for a patient. Not only severe pain 

 and inability to use the eyes for any length of time, but 

 even personal disfigurement may be produced. Thus a 

 case is recorded (p. 307) of a patient whose eyes were 

 being forced into a divergent squint by the use of pris- 

 matic glasses. After a careful examination, the prisms 

 were discarded and suitable lenses were ordered, with 

 the result that, after two weeks, complete comfort 

 and the possibility of working with satisfaction were en- 

 joyed for the first time for many years. 



Altogether this book gives us a good idea of the vast 

 advantages to the human race which have resulted from 

 the optical researches of Helmholtz, culminating in the 

 invention of the ophthalmometer and the ophthalmoscope. 



E. E. 



A Key to the Birds of Australia and Tasmania, with 



their Geographical Distribution in Australia. By R. 



Hall. Pp. xii -1- 116; plate and map. (Melbourne: 



Mullen and Slade ; London : Dulau and Co., 1899.) 



Were it nothing more than a synopsis of Australian 



birds, with just sufficient in the way of description to 



enable the different species to be easily recognised, this 



well-printed little " Key" would be to a great extent of 



merely local interest. But since the author has very 



wisely made geographical distribution its leading feature, 



the work appeals to a much wider circle of students than 



would otherwise have been the case. 



In his Report on the Zoology of the Horn Expedition, 

 Prof. Baldwin Spencer recently divided Australia into 

 three zoological sub-regions ; namely, (i) the Torresian, 

 embracing the northern and eastern districts as far as 

 South Queensland ; (2) the Barsian, comprising eastern 

 New South Wales, Victoria and Tasmania ; and (3) the 

 Eyrean, including the remainder of the mainland. These 

 sub-regions are further split up into " areas," and the 

 fact that bii"d-distribution accords with such a parcelling- 

 out of the continent from other lines of evidence affords 

 important testimony in support of Prof. Spencer's views. 

 It is noteworthy that the South Queensland area forms 

 the headquarters of the Australian Passeres, a fact for 

 which there must surely be some adequate physical 

 reason, if only it could be discovered. The total number 

 of species recorded is 767, among which the black emu 

 is believed to be extinct ; and, so far as we have been 

 able to verify them, the diagnoses of the various groups 

 and species seem well adapted to their purpose. , The 

 work appears singularly free from errors and misprints, 

 and ought to be in the hands of every Australian bird- 

 lover. R. L. 



Pages Choisies des Savants Modernes. By A. Rebi^re. 



Pp. viii -I- 620. (Paris : Nony et Cie, 1900.) 

 This is a series of extracts (translated into French when 

 not written in that language) from the works of eminent 

 men of science. It appeals mainly to the general reader, 

 and the best that can be hoped of it is that it may induce 

 some members of this class to study the works of one or 

 other man of science seriously. A scientific writer does 

 not appear to the best advantage in " tit-bits " selected 

 from his works ; and, except as a possible stimulus, the 

 value of such a miscellany as this cannot be reckoned 

 very high. The portraits, of which there is a considerable 

 number, will probably be found, by scientific readers, the 

 most interesting feature of M. Rebiere's compilation. 



