iv CONTENTS. 



On the Existence of peculiar Crystals in the Cavities of the Topaz. 

 Part I. By Sir D. Brewster, K.H.. ... 21 



On the Use of Colourless Ink in Writing. By Sir George S. Mac- 

 kenzie, Bart., . .... 21 



On the Use of Metallic Reflectors for Sextants, and on the Deter- 

 mination of the Errors arising from Non-Parallelism in the 

 Mirrors and Sun-Shades of Reflecting Instruments. By John 

 Adie, Esq., . . . . . .22 



On the Existence of peculiar Crystals in the Cavities of Topaz. 

 Part II. By Sir David Brewster, K.H., . , .23 



On the Extraction of pure Phosphoric Acid from Bones, and on a 

 New and Anomalous Phosphate of Magnesia. By Dr Gregory, 25 



On the Improvement of Navigation in Tidal Rivers. By David 

 Stevenson, Esq., ...... 26 



On the Solvent Action of Drainage Water on Soils. By John 

 Wilson, Esq., F.G.S. Communicated by Dr Gregory, . 28 



Observations on the Temperature of the Earth at Trevandrum, in 

 Lat. 8° 30' 32". By John Caldecott, Esq. Reduced, with some 

 Remarks, by Professor Forbes, . . . .29 



Miscellaneous Observations on Blood and Milk. By Dr John 

 Davy, ....... 32 



An Account of some of Mr Bain's applications of Electricity as a 

 moving power to Clocks, . . . . .33 



On Dr WoUaston's Argument from the limitation of the Earth's 

 Atmosphere as to the Finite Divisibility of Matter. By Dr 

 George Wilson, ...... 34 



Biographical Notice of the late Professor Henderson. By Profes- 

 sor Kelland, ...... 35 



On the Chemical Relations of Creosote. By Dr Gregory, . 45 



On the Thermometric Correction of Magnetic Instruments. By J. 

 A. Broun, Esq., . . .^ . . . .46 



On the Constitution of Bebeerine. By Dr Douglas Maclagan, 

 and Thomas G. Tilley, Esq., Birmingham, . . 46 



On the Sums of the Digits of Numbers. By Bishop Terrot, . 49 



Notes on the Topography and Geology of the Cuchullin Hills in 

 Skye ; and on the Traces of Ancient Glaciers which they pre- 

 sent. Part I. By Professor Forbes, . . .50 



Notes on the Topography and Geology of the Cuchullin Hills in 

 Skye ; and the Traces of Ancient Glaciers which they present — 

 (concluded). By Professor Forbes, . . . 54 



On the recent Eruption of Hecla, and the Volcanic Shower in 

 Orkney. By Dr TraiU, ..... 56 



On a new variety of Gamboge from the Wynaad. By Dr Christison, 58 



Results of the Makerstoun Observations, No. 1. On the Relation 

 of the Variations of the Earth's Magnetism to the Solar and 

 Lunar Periods. By J. A. Broun, Esq. Communicated by Sir 

 T. M. Brisbane, Bart., ..... 58 



Experiments and Investigations as to the influence exerted over 

 some Minerals by Animal and Vegetable matter, under certain 

 conditions. By Mrs Margaret Henrietta Marshall. Communi- 

 cated by Sir T. M. Brisbane, Bart., . . . 59 



