November 7, 19 12] 



NATURE 



jective coordinates, an account of the parametric 

 representation of twisted cubics and quartics, 

 Staude's elegant thread construction for confocal 

 ellipsoids, and considerable reference to the later 

 results obtained in differential geometry. There 

 are a large number of minor changes, but the 

 numbering of articles and chapters remains un- 

 altered. Mr. Rogers is to be congratulated on 

 the way in which he has executed a far from easy 

 task. 



(10) The author claims that the method ex- 

 plained in this volume abbreviates and simplifies 

 very materially the work of surveyors and naviga- 

 tors. It is, of course, impossible for us to judge 

 from a perusal of the book how far the theodolite 

 which Mr. Fergusson has invented is successful in 

 practical work. But Prof. Heath states that it 

 has been tested in the engineering department 

 of Birmingham University, and has proved ex- 

 tremely convenient. He also remarks that 



"the reduction of the results of observations can 

 be carried on simultaneously with the field work 

 without reference to books of tables, thus giving 

 the surveyor full information about any part of 

 the field observed, while he is on the spot. For 

 all traverse surveying, especially for rapid pre- 

 liminary traverse, subject to modification, the 

 instrument possesses distinct advantages over the 

 ordinary theodolite." 



The fundamental idea in the construction of the 

 instrument lies in the method of graduation. To 

 explain the system adopted, we will suppose that 

 OAy, O.AjQo are two radii of the circle, containing 

 an angle of 45°. Then points Aj, Aj, . . . Ar 

 . . . are marked on the rim such that the tangent 

 of the angle .ArOAp is equal to r/ioo, where r 

 takes all values from i to 100. By this means it 

 is clear that the obser\'er, instead of reading off 

 the angle, obtains its tangent, which is more useful 

 for his purpose. .As a matter of fact, the new 

 form of theodolite is also graduated in degrees so 

 that the angle can also be obtained, if desired. 

 The angle AjOAy is taken as unit, and is called 

 the one per cent, angle. 



The first fifty pages explain very fully the 

 theory, and numerous examples are given to show 

 its application. The remaining 450 pages are 

 occupied with tables, to the compilation of which 

 the author has given nineteen years. The leading 

 column gives the angle in the percentage form at 

 intervals of o'ooi per cent, below i per cent., and 

 of o'oi per cent, above it. The other columns 

 give logarithmic sines, cosines, tangents, secants 

 with difference tables to seven places of decimals, 

 and the angle in degrees to o'ooi of a second. A 

 shorter table at the end contains tangents of half 

 angles and versines. It seems almost incredible 

 NO. 2245, VOL. 90] 



that any one man should have been able to carry 

 through, almost single-handed, such a laborious 

 work as Mr. Fergusson has accomplished. It un- 

 doubtedly merits the serious consideration of those 

 engaged in survey work. The bulky size of the 

 volume gives it rather an alarming appearance, 

 but the processes are in reality very simple, and a 

 single hour's work with the instrument would 

 probably be enough to enable any practical inan to 

 gauge its utility. 



(11) There is a distinct need for a treatise on 

 statics suitable for candidates for entrance 

 scholarships at the universities. A number of 

 excellent introductory text-books exist, but with 

 two possible exceptions we do not know of any 

 work which exactly meets this demand. Many 

 teachers will therefore welcome the publication of 

 Prof. Loney's book, which may be regarded as a 

 companion volume to his " Dynarhics of a Particle 

 and of Rigid Bodies," recently issued. It is 

 assumed that the student possesses some know- 

 ledge of the methods of the calculus and the 

 elements of analytical solid geometry. In addition 

 to the ordinary elementary course, it contains 

 chapters on shearing stresses, three-dimensional 

 forces, wrenches, chains, attractions and potential, 

 and slightly elastic beams. There is an excellent 

 collection of examples, including some of very 

 considerable difficulty. The author has the rare 

 gift of writing simply, and he has chosen his 

 material with the same skill that characterises his 

 previous work. 



PHILOSOPHY AND PSYCHOLOGY. 

 (i) Scientific Method: its Philosophy and its 

 Practice. By F. W. Westaway. Pp. xxi -1-439. 

 (London: Blackie and Son, Ltd., 1912.) Price 

 6s. 



(2) Proceedings of the Aristotelian Society. New 

 Series. Vol. xii. Containing the Papers read 

 before the Society during the Thirty-third 

 Session, 1911-1912. Pp. ii + 345. (London: 

 \\'illiams and Norgate, 1912.) Price iojs. 6d. 

 net. 



(3) .Anales de Psicologia. Trabajos del ano 1910. 

 Volumen ii. Pp. 360. (Buenos Aires : La 

 Semana Medica. Imp. de Obras de E. 

 Spinelli, 1911.) 



(i) AN excellent book for science teachers and 

 Jr\. for the general reader who wishes "to 

 acquaint himself with scientific method. Begin- 

 ning with the consideration of words and the 

 importance of exactness in their use, Mr. West- 

 away enters on a sketchy history of philosophy, 

 dealing with Plato, Aristotle, Bacon, Descartes, 

 Locke, and Hume. Thence he proceeds to logic. 



