CONTENTS OF VOL. X. 



(FIFTH. SEEIES). 



NUMBER LIX.— JULY 1880. 



Page 

 Mr. J. Venn on the Diagrammatic and Mechanical Represen- 



tation of Propositions and Reasonings 1 



Prof. J. H. Pointing on a simple Form of Saccharimeter .... 18 

 Messrs. Morton, Mayer, and Thomas on an Incandescent 

 Paper-carbon Horseshoe Lamp constructed by Mr. T. A. 



Edison 21 



Prof. G. Quincke on Electrical Expansion 30 



Mr. J. D. H. Dickson on the Criterion by which the Critical 



Point of a Gas may be determined 40 



Messrs. Ayrton and Perry on the Determination of the Acce- 

 leration of Gravity for Tokio, Japan 43 



M. A. Kundt on Anomalous Dispersion in Incandescent Sodium 



Vapour 53 



M. C. Cellerier on a Simplification of the Theory of Vibratory 



Motions = . 57 



MM. Strouhaland Barus on a Simple Method of Galvanic Cali- 

 bration of a AVire 60 



Proceedings of the Geological Society : — 



Rev. E. Hill and Prof. T. G. Bonney on the Pre-Carboni- 



ferous Rocks of Charnwood Eorest 63 



Mr. J. H. Collins on the Geological Age of Central and 



"West Cornwall 64 



Dr. C. Callaway on a Second Pre-Cambrian Group in 



the Malvern Hills 65 



Dr. Gwyn Jeffreys on the Occurrence of Marine Shells 

 of existing Species at different Heights above the pre- 

 sent Level of the Sea 65 



Mr. J. E. Man? on the Pre-Devonian Rocks of Bohemia 66 

 Xote on the Conductivitv of Tourmaline Crvstals, bv George 



Francis Fitzgerald, M.A., F.T.C.D 67 



On a Simple Method of Identifying a Submerged Telegraph- 

 Cable without cutting it, by W. P. Johnstone 69 



Cosmical Determination of Joule's Equivalent, bv Prof. Pliny 



Earle Chase, LL.D 70 



On Substances possessing the Power of Developing the latent 



Photographic Image, by M. Carey Lea 70 



Note on the Construction of Guard-ring Electrometers, by 

 George Francis Fitzgerald, M.A., F.T.C.D. .".'..' .' . 72 



