P L A T E S. 



I. Illustrative of Mr. G. H. Berry's Paper on Pianoforte 



Bridges. 

 II. Illustrative of Prof. D. N. Mallik's Paper on Lines of Force 

 due to given Static Charges. 

 III. Illustrative of Prof. J. Joly's Paper on the Age of the 

 Earth. 

 IV. & V. Illustrative of Prof. R. W. Wood's Paper on the Resonance 

 Spectra of Iodine Vapour and their Destruction by Gases 

 of the Helium Group. 

 VI. & VII. Illustrative of Dr. J. H. Vincent's Paper on Electrical 



Experiments with Mercury contained in Tubes. 

 VIII.-XI. Illustrative of Prof. A. Trowbridge and Mr. I. B. Crandall's 

 Paper on Groove-Form and Energy Distribution of 

 Diffraction Gratings. 

 XII. & XIII. Illustrative of Prof. E. Taylor Jones and Mr. D. E. 



Roberts's Paper on the Induction Coil. 

 XIV. & XV. Illustrative of Dr. Henry Wilde's Paper on the Origin of 

 Cometary Bodies and Saturn's Rings. 

 XVI. Illustrative of Mr. C. W. Ileaps's Paper on the Effect of 

 Magnetic Fields on Metallic Resistance. 

 XVII. Illustrative "of Prof. C. T. Knipp's Paper on Rays of 

 Positive Electricity from the Wehnelt Cathode. 



E R R A T A. 



Page 175, line 4 from bottom, for Y\{u x ) read F\{u l ) = 0. 

 Page 534, line 5, for [Plates VHI.-X.] read [Plates VIII.-XI.] 

 Page 543, line A, for PI. IX. read PI. XI. 



