CONTENTS OF VOL. XXXIII. — THIIID SERIES. VII 



Page 

 Mr. J. Cockle on certain Functions resembling Quaternions, 



and on a new Imaginary in Algebra. In a Letter to T. S. 



Davies, Esq 435 



Prof. E. Wartmann's Seventh Memoir on Induction 439 



The Rev. T. P. Kirkman on Pluquaternions. and Homoid Pro- 

 ducts of Sums of n Squares 447 



Mr. W. Pringle on the Duration of a Solar Spot 460 



The Rev. J. Challis's Further investigation of the Nature of 



Aerial Vibrations 462 



Notices respecting New Books: — Messrs. H. E. Strickland and 



A. G. Melville on the Dodo and its Kindred; Mr. C. R. 



Weld's History of the Royal Society 467 



Proceedings of the Royal Astronomical Society 477 



On a simple and ready way of producing Tools for grinding 



Lenses, by N. S. Heineken, Esq 480 



Dr. Bialloblotzky's Journey to the Sources of the Nile 481 



On the Arsenites of Iron 481 



Analyses of different varieties of Epidote, by M. Hermann . . 483 



On the Preparation of Black Sulphuret of Mercury 486 



Meteorological Observations for October 1848 487 



Table 488 



NUMBER CCXXV.— SUPPLEMENT TO VOL. XXXIII. 



Sir D. Brewster on the Phaenomenon of Luminous Rings in Cal- 

 careous Spar and Beryl, as produced by tubular cavities con- 

 taining the two new Fluids 489 



The Rev. T. P. Kirkman on Pluquaternions, and Homoid Pro- 

 ducts of Sums of n Squares (concluded) 494 



Mr. Reuben Phillips on the passive state of Iron 509 



Mr. T. S. Davies on Geometry and Geometers. No. Ill 513 



MM. L. Svanberg and H. Struve on the Atomic Weight of 



Molybdenum and some of its Compounds (concluded) . . . . 524 



On a Property of the Hyperbola 546 



Proceedings of the Royal Society 548 



Calculating Cubes, by J. E. Ryff'el 551 



Analyses of the Phosphates of Manganese 551 



Discovery of Columbite in the environs of Limoges, by M. Da- 



mour 553 



On Alluaudite, — anew Phosphate of Iron, Manganese and Soda, 



by M. Damour 554 



Index 555 



