PLATES. 



I. Illustrative of Prof. Threlfall's Paper on the Electrical Properties 



of Pure Nitrogen. 



II. Illustrative of Messrs. Rubens and Snow's Paper on the Refraction 



of Rays of Great Wave-length in Rock-Salt, Sylvite, and Fluorite. 



III. Illustrative of Mr. P. Sanford's Paper on a necessary Modification 

 of Ohm's Law. 



IV. Illustrative of Messrs. Rimington and Wythe Smith's Paper on 

 Experiments in Electric and Magnetic Fields, Constant and 

 Varying. 



V. & VI. Illustrative of Dr. Carl Barus's Papers on the Fusion Con- 



stants of Igneous Rock. 



VII. Illustrative of Prof. J. Perry's Paper on Liquid Friction, 



