CONTENTS. 
PART I. 
: PAGE 
I. On the Volcanic Geology of the Vivarais (Ardéche). By Jamus D. 
Forsss, Esq., F.R.S., Sec. B.S. Ed., Professor of Natural Philoso- 
. phy in the University of Edinburgh. (With Six Plates.) : 1 
II. On a Process in the Differential Calculus, and tts application to the So- 
lution of certain Differential Equations. By the Rev. P, KELLAND, 
M.A., F.B.SS. L. & E., F.C.P.S., late Fellow of Queen’s College, 
Cambridge; Professor of Mathematics, &c.; in the University of 
Edinburgh, : 5 : ; : : . 39 
IIL. On the Constitution of Codeine and its Products of Decomposition. By 
Tuomas ANDERSON, M.D., ; 3 : F : 57 
IV. On the Equilibrium of Elastic Fluids. By Mr JamMES CLERK MaxwELL, 87 
V. Dissertation on a Peruvian Musical Instrument like the Syrina of the 
Ancients. By THomAs STEWART TratLt, M.D., F.R.S.E., Profes- 
sor of Medical Jurisprudence in the University of Edinburgh. (With 
a Plate.) . : : : : - 121 
VI. Some Remarks on the Theories of Cometary Physics. By C. Prazzt 
Smytu, Esq., F.R.S.E., F.R.AS., Professor of Practical Astrono- 
my in the University of Edinburgh, and Astronomer-Royal for 
Scotland, . : 5 ; : < A 5) ele 
VII. On the Mechanical Action of Heat, especially in Gases and Vapours. 
By Wn. J. M. RANKINE, Civil Engineer, F.R.S.E., F.R.S.S.A., 
&e., : 3 2 , s : : . 147 
VOL. XX. b 

