VI 



CONTENTS. 



XXIX. On the Determination of Heights, by the Soiling Point of Water. 

 By JAMES D. FORBES, Esq., F.R.S., Sec. R.S. Ed., and Pro- 

 fessor of Natural Philosophy in the University of Edin- 

 burgh, ......... Page 409 



XXX. On the Presence of Organic Matter in the Purest Waters from Ter- 

 restrial Sources. By ARTHUR CONNELL, Esq., Professor of Che- 

 mistry in the University of St Andrews, . . . . 417 



XXXI. On the Bebeeru Tree of British Guiana. By DOUGLAS MACLAGAN, 



M.D., F.R.S.E., . . . . ' . . . . 423 



XXXII. Geological Account of Roxburghshire. By DAVID MILNE, Esq., 



F.R.S.E., 433 



PART IV. 



XXXIII. Description of a New Self-Registering Barometer. By ROBERT 



BRYSON, F.R.S.E., . 503 



XXXIV. On the Vibrations of an Interrupted Medium. By the Rev. PHILIP 



KELLAND, M.A., F.R.SS.L. $ E., Professor of Mathematics 



in the University of Edinburgh, . . . . . 511 



XXXV. Chemical Examination of the Tagua Nut or Vegetable Ivory. 

 By ARTHUR CONNELL, Esq., Professor of Chemistry in the 

 University of St Andrews, 541 



XXXVI. Account of a Repetition of several of Dr SAMUEL BROWN'S Processes 

 for the Conversion of Carbon into Silicon. By GEORGE WILSON, 

 M.D., and JOHN CROMBIE BROWN, Esq. Communicated by the 

 Secretary, ......... 547 



XXXVII. On the Development, Structure, and Economy of the Acephalocysts 

 of Authors ; with an Account of the Natural Analogies of the 

 Entozoa in General. By HARRY D. S. GOODSIR, Conservator 

 of the Museum of the Royal College of Surgeons in Edinburgh, 561 



XXXVIII. An Analytical Discussion of Dr MATTHEW STEWART'S General 

 Theorems. By THOMAS STEPHENS DAVIES, Esq., F.R.SS.L. $ 

 Ed., F.A.S., Royal Military Academy, Woolwich, , . 573 



