CONTENTS op N° 250.— Fifth Series. 



XXI. On Magnetic Tractive Force. By E. Taylor Jones, D.Sc, 

 -Assistant Lecturer in Physics in the University College of North 

 "Wales, formerly Science Scholar of Boyal Commission for Exhibition 



of 1851 page 153 



XXII. Eesearches in Acoustics. — ~No. X. By Dr. Alfred M. 

 Mayer 168 



XXIII. On the Freezing-points of Dilute Solutions. By W. 

 Nernst and E. Abegg 196 



XXIY. On Eesultant Tones. By Professor J. D. Everett, 

 F.E.S " 199 



XXV. The Compound Law of Error. By Professor F. T. 

 Edgeworth, M.A., D.C.L 207 



XXVI. Graphical Methods for Lenses. By E. S. Cole, M.A.. . 216 



XXVII. Electro-optical Investigation of Polarized Light. By 



J. Elster and H. Geitel 218 



XXVIIL On the Production of Electrical Phenomena by the 

 Eontgen Eays. By Aug. Eighi 230 



XXIX. Notices respecting New Books : — Prof. Thompson's 

 Dynamo-Electric Machinery ; Prof. Carey Foster and Dr. 

 Atkinson's Elementary Treatise on Electricity and Magnetism, 

 founded on Joubert's ' Traite Elementaire d'^lectricite ' ; Prof. 

 Holman's Computation Eules and Logarithms, with tables of 

 other useful functions 234-235 



XXX. Intelligence and Miscellaneous Articles : — 



Black Light, by M. Gustave Le Bon 235 



*** It is requested that all Communications for this Work may be addressed, 

 post-paid, to the Care of Messrs. Taylor and Francis, Printing Office, Bed 

 Lion Court, Fleet Street, London. 



