CONTENTS of N° 251.— Fifth Series. 



XXXI. On the Influence of Carbonic Acid in the Air upon the 

 Temperature of the Ground. By Prof. Syante Akrhenius. . 'page 237 



XXXII. On the Calculation of the Conductivity of Mixtures of 

 Electrolytes. By Prof. J. G-. MacG-begor, Dalhousie College, 

 Halifax,' N.S. . . * 276 



XXXIII. Thermodynamic Properties of Air. By A. W. Wit- 

 kowski. (Plates I. & II.) 288 



XXXIY. An Analytical Study of the Alternating Current Arc. 

 By J. A. Fleming, M.A., D.Sc., F.B.S., Professor of Electrical 

 Engineering in University College, London, and J. E. Petayel . . 315 



XXXV. On the Determination of High Temperatures with the 

 Meldometer. By William Eamsat, Ph.D., E.E.S., Professor of 

 Chemistry, University College, London, and N. Eumohfopottlos, 

 B.Sc, Demonstrator of Physics, University College, London 360 



XXXVI. The Magnetic Field of any Cylindrical Coil. By W. 



H. Eyekett, B.A 367 



XXXVII. A Method of Determining the Angle of Lag. By 

 Aethub L. Clark, S.B., Professor of Mathematics and Physics, 

 Bridgton Academy, North Bridgton, Maine, U.S. A 369 



XXXVIII. A Note on Mr. Burch's Method of Drawing Hyper- 

 bolas. By F. L. O. Wadsworth, E.M., M.E., Assistant Professor 



of Physics, University of Chicago . . . <. 372 



XXXIX. A Duplex Mercurial Air-Pump. By E. W. Wood . . 378 



- XL. Intelligence and Miscellaneous Articles : — 



Notes of Observations on the Eontgen Eays, by H. A. Bow- 

 land, N. E. Carmichael, and L. J. Briggs 381 



Note on " Focus Tubes " for producing X-rays, by E. W. Wood 382 



Note on Elementary Teaching concerning Focal Lengths, by 

 E. H. Barton 383 



Solution and Diffusion of Certain Metals in Mercury, by W. 

 J. Humphreys 384 



*&* It is requested that all Communications for this Work may be addressed, 

 post-paid, to the Care of Messrs. Taylor and Francis, Printing Office, Eed 

 Lion Court, Fleet Street, London. 



