Contents . 
vii 
On the Parallel Roads of Glen Roy. By the Rev. Thomas Brown, 
F.R.S.E., .339 
Note on the Perception of Musical Sounds. By John G. M ‘Kendrick, 
M.D., 342 
On the Establishment of the Elementary Principles of Quaternions 
on an Analytical Basis. By G. Plarr, Esq. Communicated by Pro- 
fessor Tait, ........ 348 
Preliminary Note “ On a New Method of obtaining very perfect 
Vacua.” By Professor P. G. Tait and James Dewar, Esq., . 348 
Laboratory Notes. By Professor Tait — 
1. On Atmospheric Electricity, .... 349 
2. On the Thermo-Electric Position of Sodium, . . 350 
On the Resistance of the Air to the Motion of Fans. By James C. 
Fairweather, Esq. Communicated by George Forbes, Esq. (With 
two Plates), . ...... 351 
On the Curve of Second Sines and its Variations. By Edward Sang, 
Esq., ........ 356 
Laboratory Notes. By Professor Tait — 
On the Thermo-Electric Positions of Sodium and Potassium, . 362 
On a New Form of Mariner’s Compass. By Sir William Thomson, . 363 
Further Note on Spectra under exceedingly Small Pressures. By 
Professor Tait and James Dewar, Esq. , . . . . 363 
On the After-Glow of Cooling Iron at a Dull-Red Heat. By George 
Forbes, Esq., ....... 363 
On a Form of Radiation Diagram. By George Forbes, Esq., . 366 
On the Semicircular Canals of the Internal Ear. By Professor Crum- 
Brown, . . . . . . . . 370 
On Last-Place Errors in Vlacq’s Table of Logarithms. By Edward 
Sang, Esq., . . . . . . . .371 
Note on the Submerged Fossil Trees of Granton Quarry. By Sir 
Robert Christison, Bart., Hon. V.P. R.S.E., . . . 377 
Note on Grouse Disease. By Professor Maclagan, . . . 378 
Latent Heat of Mercury Vapour. By James Dewar, Esq., . .380 
Notes by James Dewar, Esq. — 
1. Problems of Dissociation, ..... 380 
2. Formation of Allotropic Sulphur, .... 380 
3. Heat of Fermentation, ..... 380 
Further Note on Continuants. By Thomas Muir, M.A., F.R.S.E., 
Assistant to the Professor of Mathematics in Glasgow University, 380 
On the Formation of Allotropic Sulphur. By James Dewar, Esq., . 382 
On Some Compounds of Dimethyl-Thetine. By Professor Crum- 
Brown and Dr E. A. Letts, . . . . . 382 
On a New Example of the Opheliidse ( Linotrypane apogon ) from 
Shetland. By W. C. MTntosh, M.D., .... 386 
Concluding Remarks by David Milne Home, LL.D., . , „ 390 
