CONTENTS. 

 VOL. III. 



1830. 



On the Nature of Negative and Imaginary Quantities. By Davies Gil- 

 bert, Esq. President of the Royal Society page 4 



On a simple Electro-chemical Method of ascertaining the presence of 

 different Metals ; applied to detect minute quantities of Metallic 

 Poisons. By Edmund Davy, Esq. F.R.S. M.R.I. A. and Professor 

 of Chemistry to the Royal Dublin Society 5 



On the performance of Fluid Refracting Telescopes, and on the appli- 

 cability of this principle of construction to very large instruments. 

 By Peter Barlow, Esq. F.R.S. Corresponding Member of the Insti- 

 tute of France, of the Imperial Academy of St. Petersburg, &c 13 



Researches in Physical Astronomy. By John William Lubbock, Esq. 

 V.P. and Treasurer of the Royal Society 16 



On the Hour Lines of the Ancients. By W. A. Cadell, Esq. F.R.S. 18 



1831. 



On the Equilibrium of Fluids ; and the Figure of a Homogeneous 



Planet in a fluid state. By James Ivory, Esq. M.A. F.R.S 20 



On the probable Electric Origin of all the Phenomena of Terrestrial 

 Magnetism ; with an illustrative experiment. By Peter Barlow, 

 Esq. F.R.S. Corr. Mem. Inst. France and of the Imp. Acad. St. 

 Petersburg 23 



On the Lunar Theory 25 



On a New Combination of Chlorine and Nitrous Gas. By Edmund 

 Davy, Esq. F.R.S. M.R.I.A Professor of Chemistry to the Royal 

 Dublin Society 27 



On the Chemical Action of Atmospheric Electricity. By Alexander 

 Barry, Esq. F.L.S . 29 



An Account of Operations carried on for ascertaining the Difference 

 of Level between the River Thames at London Bridge and the Sea 



a 2 



