LIST OF ILLUSTRATIONS. 
Plates 1 to 3.—Mr. H. M‘Leod and Lieutenant G. S. Clarke on the Determination 
of the Rate of Vibration of Tuning-Forks. 
Plates 4 and 5.—Professors W. E. Ayrton and J. Perry on the Contact Theory of 
Voltaic Action. 
Plates 6 and 7.—Mr. W. Bevan Lewis on the Comparative Structure of the Cortex 
Cerebri. 
Plates 8 to 10.—Messrs. W. De La Rue and H. W. Muller on the Electric Discharge 
with the Chloride of Silver Battery. 
Plates 11 to 13.— The Earl of Rosse on some recent Improvements made in the 
Mountings of the Telescopes at Birr Castle. 
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 Rano-e 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. 
Plates 34 to. 38. —Professor Owen on some Remains of the Gigantic Land-Lizard from 
Australia. 
Plate 3.9. —Professor Owen on the Ova of the Echidna Hystrix. 
Plates 40 to 52. —Dr. C. W. Siemens on the Dynamo-electric Current, and on Certain 
Means to Improve its Steadiness. 
