280 Notices respecting New Books. 



such a cell is very long in making its appearance — so long, in fact, 

 that we may be pardoned for regarding it as we should do the 

 philosopher's stone or the elixir of life — things highly desirable, 

 perhaps, but impossible of attainment. 



Mr. Cooper's book is certain to appeal to a wide circle of readers, 

 and we have no doubt whatever that it will at once take its place 

 as the standard treatise on the subject. 



G hmeirographie ou Art dps Constructions Geomstriques. Par 

 Emilb Lemoine. C. Naud, 1902. Pp.87. ("S.ientia" 



Series, No. 18.) 



Most problems in geometrical construction admit of more than 

 one solution, but among them there is generally one which involves 

 the least number of operations, and is therefore the simplest. 

 This simplest solution constitutes the geometrographic construction. 

 The instruments employed consist of a straight-edge, dividers, 

 and set-square. The various operations involved— adjusting the 

 straight-edge so that it passes through one or two given points, 

 drawing a straight line, setting the dividers to a given length, 

 drawing a circle, &c. — are denoted by symbols. The complexity 

 of the solution may then be ascertained from the symbolical 

 expression for the operations involved, and the number of these 

 latter is termed the coefficient of simplicity (as the author properly 

 points out, the coefficient of complexity would be a more appro- 

 priate term). By a careful study of the problem, the author has 

 in many cases succeeded in reducing considerably the coefficient 

 of simplicity. One case is mentioned in which, by the joint 

 efforts of a number of geometers, this coefficient was reduced from 

 78 (involving the tracing of 17 straight Hues and 20 circles) to 35 

 (7 straight lines and 5 circles). The author gives the solutions of 

 69 problems, in some cases giving several solutions one of which 

 (the simplest") is the geometrographic one. The construction is 

 first explained, and is then followed by a symbolical formula, the 

 coefficient of simplicity, and the number of straight lines and 

 circles drawn in the course of the construction. 



Theorie de la Lune. Pur H. A^doyeb,. Paris : C. Naud, 

 1902. Pp. 86. (" Scientia" Series, No. 17.) 



Itf this little book, the author develops, in the simplest possible 

 form, the principal portions of the lunar theory, without, however, 

 considering the numerical values of the various constants which 

 appear in the equations. On account of the highly abstruse 

 nature of the subject, the book is necessarily intended for 

 specialists, and to them should prove very useful. 





