CONTENTS. Vll 



Page 

 Mr. J. Booth on the Focal Properties of Surfaces of the Second 



Order 432 



Address of the General Secretaries of the British Association, 



R. I. Murchison, Esq. and Major E. Sabine 441 



Dr. C. Schafhaeutl's Remarks on the Electricity of Steam. . . . 449 

 Mr. W. G. Armstrong on the Electricity of Effluent Steam. . . . 452 

 Mr. H. L. Pattinson's Further Experiments on the Electricity 



of Steam 457 



The Rev. J. Challis on the Motion of a small Sphere vibrating 



in a resisting Medium 462 



Mr. Lubbock on the Heat of Vapours and on Astronomical 



Refractions {continued) 467 



Proceedings of the Royal Geological Society of Cornwall; 



Twenty- Seventh Annual Report of the Council 474 



Atomic Weight of Carbon 477 



Pyrrhite — a new Mineral 478 



Pihlite — a new Mineral 479 



Dysodil 479 



Meteorological Observations for October, 1840 479 



Table 480 



NUMBER CXIIL— SUPPLEMENT TO VOL. XVII. 



G. B. Airy, Esq., Astronomer Royal, on Professor Challis's 

 Investigation of the Motion of a Small Sphere vibrating in 



a Resisting Medium , 481 



Address of the General Secretaries of the British Association, 



R. I. Murchison, Esq. and Major E. Sabine {concluded). . . . 482 

 Mr. Lubbock on the Heat of Vapours and on Astronomical 



Refractions (concluded) 488 



Proceedings of the Geological Society 508 



Blue Oxide of Titanium 542 



Chelidonia and Pirropina 543 



Index 545 



PLATES. 



I. Illustrative of Mr. Griffith's Paper on the Mineral Structure of 



the South of Ireland. 



II. Illustrative of Dr. Faraday's Letter to M. Gay-Lussac, on Magneto- 



electric Induction*. 



* This Plate will be given in one of the Number of the next Volume. 



