Contents. 
IX 
The application of the Graphic Method to the determination of the 
efficiency of a direct-acting Steam-Engine. By Professor Fleeming 
Jenkin, ........ 563 
On the Disruptive Discharge of Electricity. By Alexander Macfar- 
lane, M.A., B.Sc. Communicated by Professor Tait, . . 563 
On the Compressibility of Water, Sea- Water, a four per cent. 
Chloride of Sodium Solution, Mercury, and Class. By J. Y. 
Buchanan, M.A., F.R.S.E., ..... 565 
On the Action of Heat on some Salts of Trimethyl-Sulphine. By 
Professor Crum Brown and J. Adrian Blaikie, Esq., . . 565 
Extracts from two letters on the Refractive Indexes of Glass and 
Quartz, as tested by Reflection from the Surface. By Professor 
Quincke. Communicated by Sir William Thomson, . . 567 
Mr Gott’s and Professor Bell’s Explanation of the Action of the 
Telephone, . . . . . . . .570 
Proposed Theory of the Progressive Movement of Barometric Depres- 
sions or Storms ; being in continuation of the Paper read before 
the Society on July 5, 1875. By Mr Robert Tennent, . .570 
On the Thermo-Electric Properties of Charcoal and certain Alloys, 
with a supplementary Thermo-Electric Diagram. By C. G. Knott, 
B.Sc., and J. G. MacGregor, D.Sc. Communicated by Professor 
Tait, . . . . . . . .579 
On the Auriferous Quartz of Wanlockhead. By Dr Lauder Lindsay, 579 
On the Discharge of Electricity through Turpentine. By A. 
Macfarlane, B.Sc., and Mr R. J. S. Simpson. Communicated by 
Professor Tait, . . . . . . .579 
Remarks on the Phonograph. By Professor Fleeming Jenkin and 
Mr J. A. Ewing, . . . . . . .579 
On Thermal Conductivity. By Professor Tait, . . .581 
On the Wave Forms of Articulate Sounds. By Professor Fleeming 
Jenkin and Mr J. A. Ewing, ..... 582 
On the Action of the Chlorides of Iodine upon Acetylene and 
Ethylene. By George M‘Gowan, ..... 588 
On some Definite Integrals. By Professor Tait, . . . 594 
Chapters on the Mineralogy of Scotland. Chapter IV. — Augite 
Hornblende, and Serpentinous Change. By Professor Heddle, . 595 
On the Old Red Sandstone of Western Europe. By Professor 
Geikie, F.R.S., . . . . . . .596 
On Beats of Imperfect Harmonies. By Sir William Thomson, . 602 
On Vortex Vibrations, and on Instability of Vortex Motions. By 
Sir William Thomson, . . . . . .613 
On the Theory of Vowel Sounds. By Professor M‘Kendrick, . 613 
Preliminary Note on a Method of Detecting Fire-Damp in Coal 
Mines. By Professor George Forbes, . . . .613 
Note on Electrolytic Conduction. By Professor Tait, . .614 
Note on Thermal Conduction. By Professor Tait, . . .615 
h 
