LIST OF ILLUSTRATIONS. 
Plate 1 . —Dr. A. Schuster on the Spectra of Metalloids. 
Plates 2 to 13.—Sir William Thomson on the Electrodynamic Qualities of Metals. 
Plate 14. —Mr. W. Crookes on the Illumination of Lines of Molecular Pressure, and 
the Trajectory of Molecules. 
Plates 15 to 20.—Messrs. W. Spottiswoode and J. Fletcher Moulton on Electrical 
Discharges through Rarefied Gases. 
Plates 21 to 34.—Messrs. W. N. Hartley and A. K. Huntington on the Action of 
Organic Substances on the Ultra-violet Rays of the Spectrum. 
Plate 35. —Mr. J. B. Hannay on the Microrheometer. 
