680 Notices respecting New Books. 



The Elementary Differential Geometry of Plane Curves. By 

 R. H. Fowler, M.A. Cambridge University Press. Cambridge 

 Tracts, No. 20. 1920. 8vo, pp. viii + 105. Price 6s. net. 



This tract gives a concise but clear and rigorous presentation of 

 the differential properties of plane curves. Tangents and Normals, 

 Curvature, Theory of Contact, Theory of Envelopes, Singular 

 Points, and Asymptotes of plane curves are the subjects of its 

 chapters JI. to VII. The first chapter gives a good analytical 

 Introduction to the subject. This excellent tract deserves the 

 attention of all students of mathematics. 



Lectures on the Theory of Plane Curves, delivered to post-graduate 

 students in the University of Calcutta. By Sttremdranshan 

 G-anganli, M.Sc. Published by the University of Calcutta, 

 1919. 8vo. Pp. vi + 350 + 17 (diagrams), in two Parts. 



Contents : Introduction (on homogeneous coordinates, the line 

 at infinity, line-coordinates, circular points at infinity, projection). 

 Theory of plane curves. Singular Points. Polar Curves. Co- 

 variant Curves ; the Hessian Polar Reciprocal Curves. Eoci of 

 Curves. The Analytical Triangles ; Asymptotes. System of 

 Curves (pencil of curves, envelopes, etc.). Cubic Curves (Chapters 

 X.-XV.). Curves of the 4th order (Chapters XVI.-XX.). 

 Appendix I, Notes on the Bicircular Quartic. Appendix II, Note 

 on Trinodal Quartics. 



This handy and easily readable work will be particularly helpful 

 to those interested in cubics and quartics, which are treated very 

 fully in the last eleven chapters. 



Editorial Note. 



IN the February issue of the Philosophical Magazine we pub- 

 lished a paper by Mr. Norman Campbell on " The Adjustment 

 of Observations." That paper was intended to be followed by two 

 others in which the reasons for the contentions advanced in the 

 first would be given. We now discover that the second paper 

 of the series, which Mr. Campbell imagined to be in our hands, 

 has gone astray and cannot therefore be published. Mr- Campbell 

 a-ks us to state that the substance of the second and third papers 

 is to be found in his book 'Physics — The Elements ' just pub- 

 lished by the Cambridge University Press. It will be seen from 

 that book that he does not accept the assumptions on which 

 Dr. Meld rum Stewart, in the April issue of this Journal, based 

 a criticism of the first paper. W. Erancis. 



