VI CONTENTS OF VOL. XXVIII. —FIFTH SERIES. 



The Energy of Thermal Eadiation at a White Heat, by 0. 

 Tumlirz and A. Krug 352 



Calculation of the Mechanical Equivalent of Light from the 

 Experiments of Julius Thomsen, by O. Tumlirz 352 



NUMBER CLXXIY.— NOVEMBEE. 



Prof. E. Threlfall and Mr. A. Pollock on the Clark Cell as a 



Source of small Constant Currents. (Plates XII. & XIII.) 353 

 Mr. C. Tomlinson on Lightning and Gunpowder Magazines. 368 



Prof. E. Wiedemann on the Mechanics of Luminosity 376 



Mr. Magnus Maclean on Elementary Nomenclature in Geo- 

 metrical Optics 400 



Mr. S. A. Sworn on the Constitution of the Aromatic Nucleus. 402 

 Prof. Eichard Threlfall on the Application of the Clark Cell to 

 the Construction of a Standard Galvanometer. (Plate XIV. 



figs. 1 & 2) 416 



Mr. H. S. Carhart on an Improved Standard Clark Cell with 



Low Temperature-Coefficient 420 



Notices respecting New Books : — 



Watts's Dictionary of Chemistry, Vol. II 423 



Dr. A. Bernthsen's Text-Book of Organic Chemistry. . . . 424 

 Eev. Isaac Warren's Elementary Treatise of Mechanics. 425 

 On aEelation between the Sun-spot Period and the Planetary 



• Elements, by Charles Davison 426 



On the Leakage of Negative Electricity caused by Sun- and 



Daylight, by T. Elster and H. Geitel 427 



On the Phosphorescence of Copper, Bismuth, and Manganese 

 in the Sulphides of the Alkaline Earths, by V. Klatt and 



Philipp Lenard 428 



On Steatite as a Source of Electricity, by M. Mentzner .... 428 



NUMBEE CLXXV.— DECEMBEE. 



Mr. Charles H. Lees on the Law of Cooling, and its bearing on 

 certain Equations in the Analytical Theory of Heat 429 



Mr. S. A. Sworn on the Constitution of the Aromatic Nucleus 443 



Prof. E. Threlfall on the Measurement of High Specific 

 Eesistances (Plate XIV. fig. 3) 452 



Prof. Eichard Threlfall and Mr. A. Pollock on Measure- 

 ments of the Eesistance of Imperfectly Purified Sulphur. . 469 



