LIST OF ILLUSTRATIONS. 
Plates 14 to 21. —Professor W. C. Williamson on the Organization of the Fossil 
Plants of the Coal-Measures. 
Plates 22 to 24. —Mr. W. Ellis on the Relation between the Diurnal Range of 
Magnetic Declination and Horizontal Force and the Period of Solar Spot 
Frequency. 
Plates 25 to 29.— Messrs. W. Spottiswoode and J. Fletcher Moulton on the 
Sensitive State of Vacuum Discharges. 
Plates 30 to 32. —Captain W. de W. Abney on the Photographic Method of Mapping 
the least Refrangible End of the Solar Spectrum. 
Plate 33.— Dr. W. Huggins on the Photographic Spectra of Stars. 
