CONTENTS. 



PAGE 



Art. I. Biographical Sketch of James Cowles Prichard, 

 M.D., F.R.S., Corresponding Member of the In- 

 stitute of France, «S:c., late President of the Ethno- 

 logical Society, and Author of " Researches into 

 the Physical History of Man." By Thomas 

 HoDGKiN, M.D., 205 



II. A Description of several extraordinary Displays of 



the Aurora Borealis, as observed at Prestvvich, 

 during the winter of 1848-1849 ; with Theoreti- 

 cal Remarks. By William Sturgeon, Lecturer 

 on Natural and Experimental Philosophy, formerly 

 Lecturer at the Honourable East India Company's 

 Military Academy, Addiscombe, and late Editor of 

 the "Annals of Electricity," &c. Communicated by 

 the Author. (Concluded from p. 158), . . 225 



III. On a Formula for calculating the Expansion of Li- 



quids by Heat. By William John MAcauoRN 

 Rankine, Civil Engineer. Communicated by the 

 Author, . 235 



IV. On the Geographical Distribution and Uses of the 



Common Oyster (Ostrca cdulis), . . . 239 



V. Comets — Great Number of Recorded Comets — The 

 Number of these unrecorded probably much greater 

 — General Description of a Comet — Comets with- 

 out Tails, or with more than one — I'heir extreme 

 Tenuity — Their probable Structure — Motions 



