Perturbations of the Leonids. 



403 



Salomons, Sir David, M.A. 



Saunders, Edward. 



Schlich, Professor William, C.I.E. 



Sell, William James, M.A. 



Shaw, Professor Henry S. Hele, 

 M.Inst.C.E. 



Sidgreaves, Rev. Walter, S.J. 



Smith, James Lorrain, M.D. 



Smith, Professor William Robert, 

 M.D. 



Smithells, Professor Arthur, B.Sc. 



Spencer, Professor W. Baldwin, B. A. 



Starling, Ernest Henry, M.D. 



Swinton, Alan Archibald Camp- 

 bell, Assoc. M.Inst.C.E. 



Tanner, Professor Henry William 

 Lloyd, M.A. 



Tatham, John F. W., F.E.C.P. 



Thomas, Michael Rogers Oldfield, 

 F.Z.S. 



Threlfall, Professor Richard. 



Tutton, Alfred E., B.Sc. 



Ulrich, Professor George Henry 

 Frederic, F.G.S. 



Walker, James, M.A. 



Walker, Professor James, D.Sc. 



Watson, William, B.Sc. 



Whitehead, Charles, F.L.S. 



WTiymper, Edward, F.R.G.S. 



Windle, Bertram Coghill Allen, 

 M.D. 



Woodward, Arthur Smith, F.G.S. 



Wright, Professor Edward Per- 

 ceval, M.A. 



The following Papers were read : 



I. "Perturbations of the Leonids." By Dr. G. J. STONEY, F.R.S. 

 and Dr. DOWNING, F.R.S. 



II. " On Flapping Flight of Aeroplanes." By Professor M. F. FITZ- 

 GERALD. Communicated by Professor G. F. FITZGERALD, F.R.S. 



III. " On Hydrogen Peroxide as the Active Agent in producing Pictures 

 on a Photographic Plate in the Dark." By Dr. J. W. RUSSELL, 

 F.R.S. 



" Perturbations of the Leonids." By G. JOHNSTONE STONEY, M.A., 

 D.Sc., F.R.S., and A. M. W. DOWNING, M.A, D.Sc., F.R.S. 

 Received February 8, Read March 2, 1899. 



When the present investigation was undertaken, our knowledge of 

 the perturbations of the Leonids was due to an investigation carried 

 on thirty years ago by Professor J. C. Adams.* 



His object was to compute the shift in the nodes of the meteoric 

 orbit due to perturbations, and to compare the calculated amount with 

 the amount which had been deduced by Professor Hubert A. Newton 

 from observations made at intervals during the last 1000 years.! 



For Professor Adams's purpose the perturbations to be computed 



* ' Comptes Kendus,' March 25, 1867, p. 651 ; and for a fuller account see 

 'Monthly Notices of the Eoy. Astron. Soc.,' April, 1867, p. 247; or 'Monthly 

 Notices,' March, 1897, p. 387, where the last-mentioned paper is reprinted. 



t ' Silliman's Journal,' 1864, vol. 37, p. 377 ; and vol. 38, p. 53. 



