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 Some Measures of Young's Modulus for Crystals, &c. By A. Mallock.... 380 



On the Chief Line in the Spectrum of the Nebulae. By James E. 

 Keeler, Astronomer of the Lick Observatory 399 



List of Presents.... ... 403 



No. 300. April 9, 1891. 



On Electrostatic Screening by Gratings, Nets, or Perforated Sheets of 

 Conducting Material. By Sir William Thomson, D.C.L., P.R.S 405 



On Variational Electric and Magnetic Screening. By Sir William 

 Thomson, P.E.S 418 



The Measurement of the Power given by any Electric Current to any 

 Circuit. By W. E. Ayrton, F.R.S., Professor of Applied Physics in 

 the City and Guilds of London Institute, and W. E. Sumpner, D.Sc 424 



On Galvano-Hysteresis. (Preliminary Notice.) By Silvanus P. Thomp- 

 son, D.Sc., B.A., Professor of Physics in the City and Guilds Technical 

 College, Finsbury 439 



List of Presents.... .. 440 



April 16, 1891. 



On the Causes which produce the Phenomena of New Stars. By J. 

 Norman Lockyer, F.R.S 443 



An Attempt to determine the Adiabatic Relations of Ethyl Oxide. 

 Part I. Gaseous Ether. By W. Ramsay, F.R.S., Professor of Che- 

 mistry in University College, London, and E. P. Perman, B.Sc 447 



On the Physical Characters of the Lines in the Spark Spectra of the 

 Elements. By W. N. Hartley, F.R.S., Professor of Chemistry, Royal 

 College of Science, Dublin 448 



List of Presents.... 452 



April 23, 1891. 



Contributions to the Chemical Bacteriology of Sewage. By Sir Henry 

 E. Roscoe, F.R.S., D.C.L., LL.D., and Joseph Lunt, B.Sc., F.C.S 455 



Note on the Instability of India-rubber Tubes and Balloons when dis- 

 tended by Fluid Pressure. By A. Mallock 458 



List of Presents . 463 



April 30, 1891. 



Cloud Photography conducted under the Meteorological Council at the 

 Kew Observatory. By Lieutenant-General R. Strachey, R.E., F.R.S., 

 and G. M. Whipple, Superintendent of the Observatory 467 



The Passive State of Iron and Steel. Part III. By Thos. Andrews, 

 F.R.SS.L. and E., M.Inst.C.E 481 



On the Demonstration of the Presence of Iron in Chromatin by Micro- 

 chemical Methods. By A. B. Macallum, M.B., Ph.D 488 



List of Presents . ....: 489 



