624' 



INDEX. 



Wood (Miss E. M. R.) on the Lower 

 Ludlow formation, 265. 



Wood (Prof. It. W.) on the photo- 

 graphy of sound-waves, and the 

 lunematographic demonstration of 

 the evolutions of reflected wave- 

 fronts. 148 ; on an application of 

 the method of striae to the illumi- 

 nation of objects under the micro- 

 scope, 347. 



.r-rays, on the production of, by a 



battery current, 132. 

 Yield-point, on the, as the criterion 



of strength, 73. 

 Young (Prof. S.) on the law of 



Oailletet and Mathias and the 



critical density, 291. 

 Zinc, on the arc spectrum of, 502. 

 Zinc-copper alloys, on the action of,' 



on nitric acid, 231. 



END OF THE FIFTIETH VOLUME. 



Printed by Xaylok and Francis, Red Lion Court, Fleet Street, 



