CONTENTS. Ill 



PAOK 



Art. XVIII. A New Theory of the Central Heat of the Earth, 

 and of the cause of Volcanic Phenomena. By 

 Mr Stevenson Macadam, Teacher of Chemistry, 

 Philosophical Institution, Edinburgh. Communi- 

 cated by the Author, . . . . 127 



XIX. Observations made on a Voyage from Leith to 

 Grenada. By Patrick Gillespie, Commander 

 of the Barque, Marli of Leith, . . . 138 



XX. On the Chemical Constitution of the Rocks of the 

 Coal Formation. By Hugh Taylor, Esq. 

 Communicated by the Author, . . 140 



XXI. On the Tetramorphism of Carbon. By Henry 

 Clifton Sorby, Esq., E.G.S. Communicated by 

 the Author, 149 



XXII. On the alleged evidence for Physical Connection be- 

 tween Stars forming Binary or Multiple Groups, 

 deduced from the doctrine of Chances. By James 

 D. Forbes, F.R.S., Corr. Memb. of the Institute 

 of France. Communicated by the Author, . 159 



XXIII. Probable Effects of Vegetation on Climate, . 161 



XXIV. Fossil Eggs of Snakes in the Fresh- water Limestone 



at Beiber, near Offenbach. By Professor Blum, 165 



XXV. Sixteenth Letter on Glaciers. Addressed to Pro- 



fessor Jameson, 167 



(1.) Observations on the movement of the Mer de Glace, 

 down to 1850. (2.) Observations by Balraat, in 

 continuation of those detailed in the Fourteenth 

 Letter. (3.) On the gradual passage of Ice into 

 the Fluid State. (4.) Notice of an undescribed 

 Pass of the Alps. 



XXVI. Astronomical Notices. By C. Piazzi Smyth, Esq., 



F.R.S.E., Professor of Astronomy in the Univer- 

 sity of Edinburgh, . . . . 174 



