PLATES. 



I. Illustrative of Mr. W. Baily's Paper on a new Automatic Motion for 

 the Spectroscope. 



II. Illustrative of Professors W. E. Ayrton and J. Perry's Paper on Ice 

 as an Electrolyte. 



III. Illustrative of Mr. W. M. Hicks's Paper on some Effects of Dissocia- 

 tion on the Physical Properties of Gases. 



