ERRATUM IX VOL. XI. 

 Page 414, for E. H. Xichols read E. L. Xichols. 



ERRATA IX VOL. XII. 



Page 370, second line from bottom, for maximum velocity read maximum 

 rate of change of velocity 



— 871, second line from top, /or kinetic energy read acceleration 



ERRATA LX VOL. XIII. 



Pa?e 45, end of art. 45, for +e 2 read — e 2 



3 3 



— 46, art. 50, line 6, end of numerator for ~ read — J 



— 46, art. 52, line 4, for (13) read /TD) 2 s+ar , F(I)) 2 2=0 . (14) 



— 46, art. 52, line 5, for (13) read (14). 



e e c 



— 135, last line of text, in equation (7), for xr read xr 



PLATES. 



I. Illustrative of Mr. L. Wright's Paper on some Spiral Figures 

 observable in Crystals, illustrating the Relation of their Optic 

 Axes. 

 II. Rlustrative of Mr. T. Bayley's Paper on the Connexion between 

 the Atomic Weight and the Chemical and Physical Properties 

 of Elements. 

 III., IV. Illustrative of Mr. C. Vernon Boys's Paper on Integrating and 

 other Apparatus for the Measurement of Mechanical and Elec- 

 trical Forces. 



V. Rlustrative of Mr. C. Vemon Boys's Paper on Apparatus for 



Calculating Efficiency. 

 VI. Rlustrative of Mr. J. B. Hannay's Paper on Examination of 



Vacua. 

 VII. Illustrative of Messrs. Roberts and "Wrightson's Paper on the 



Fluid Density of certain Minerals. 

 Vni. Rlustrative of Mr. W. Le Conte Stevens's Papers on Physiolo- 

 gical Perspective, and on an Adjustable and Reversible Stereo- 

 scope. 



IX. Illustrative of Dr. W. Spottiswoode's Paper on a Separator and a 



Shunt for alternate Currents of High Tension. 

 X. Rlustrative of Mr. L. Fletchers Crystallographic Xotes. 



