June, 1902.] 



KNOWLEDGE. 



121 



Founded by RICHARD A. PROCTOR. 



Vol. XXV.] 



LONDON: JUNE, 1902. 



[No. 200. 



CONTENTS. 



The Vibration Produced by the Working of the Traffic 

 on the Central London Railway. B_v Chari.ks 

 Dam-OS, >c i>., F. (5. s. (Itlustraled) ... ' 



Across Russian Lapland in Search of Birds. — III. 

 Forest, Lake and Marsh. B_v Hakrt F. Withebbt, 

 F./.S.. M Il.O r {llluntrnted) ... ... 



Vegetable Mimicry and Homomorphism. — III. By Rev. 

 Alkx. S. Wn.soN, .M..\ , B s. {Illu-ilrnted) ..." 



Astronomy without a Telescope. XIV. — Sunspots 

 and Moonspots. Bv K. Walter MArxDER, f.k.a.s. 

 (UhLsfraleJl '. 



The Belt and Sword of Orion, By .Alexander Smith. 

 (Pla/f) 



Letters : 



FAHEENnEiT's Thermometer. By Sir Samuel Wilks, 

 U.l>., LI..D., p.B .s. ... 



The Visibilitv of the Cresce.nt of Venus. By Edwin- 

 Holmes. Note by E. AValter Maunder 



The Use of ITakd Telescopes in A.stroxomt. By 



F. AV. Lbvandeb 



British Ornithological Notes. Conducted by W. 1'. 



PyCBAFT, A.L.S., F.Z.S., Jf.B.O.U 



Notes 



Notices of Books 



Books RKri;:vED 

 The Nobodies, — A Seafaring Family.- III. By Rev. 



T. K. R Stebbixo, ma., f.bs.. f.l.s. (Illitstrateil) 



Microscopy. Conduct«l by M. I. Cross 



Notes on Comets and Meteors. By W. F. Dennino, 



F.R.A.-i. ... 



The Face of the Sky for June. 

 F.E.A.S. (lUust'ai.ed.) 



Chess Column. By C. D. Locock, b.a. 



By W. Shackleton, 



123 

 127 



129 

 131 



131 



132 



133 



133 

 1.33 

 135 

 137 



137 

 141 



THE VIBRATION PRODUCED BY THE 



WORKING OF THE TRAFFIC ON THE 



CENTRAL LONDON RAILWAY. 



Bv Chaui.es Uavison, Sc.D., f.g.s. 



In .Tanuary, 1901, a Committee, eonsistiusj of Lord 

 Ka_vleii,'li, Sir J. Wolfe Barrv, and Professor J. A. Ewing, 

 was appointed bv the Board of Trade " to consider and 

 report to what extent the worldng of the traific on the- 

 Central London Railway ]iroduces vibrations in the ad- 

 jacent liniklings, and wliat alterations in the condition of 

 snrh working or in structure can Iw devised to remedy the 

 same " The report of the Committee was presented last 

 January, and was followed in April by the publication of a 

 series of appendices by Mr. A. Mallock, in which the 

 details of the experiments are descril>ed, The present 



pa;)er contains a summary of the methods employed by 

 the investigators and of the results at which they arrived. 



The Committee first heard the evidence of several 

 residents near the line, who all agreed as to the objection- 

 able character of the vibrations, and then ascerta,ined by- 

 personal observation that their complaints were well- 

 founded. As the disturbances arising from successive 

 trains were found tt) vary much in intensity, concerted 

 observations were also made by about a dozen per.sons 

 stationed in diffei'ent houses near the railway-line. 

 Lastly, ^Ir. A. Mallock was deputed to make a careful 

 study of the nature and extent of the vibration ; and it is 

 tfl his scientific insight and perseverance that the Com- 

 mittee attributes in great part the successful solution of 

 the problem set before them. 



Experimeuts were first made with a seismometer thxt 

 recorded mechanically and magnified the movements of the 

 ground or floor ten times. But, this being found in- 

 sufficient, another instrument was used that recorded 

 photographically and had a magnifying power of 75. 



The principle of this instrument is the same as that 

 employed in vertical-component seismographs A weight 

 is suspended by a spring from a supjiort connected with 

 the framework of the apparatus, and is so arranged that 

 the period of the suspended weight is long compared with 

 that of the vibration to be measured. When the ground 

 or floor moves, the weight either remains practically at 

 rest or its movement is shown on the record as long oscil- 

 lations ou which the rapid vibrations of the ground and 

 point of support are superposed (Figs. 3 and 4). 



The essential part of the apparatus is shown in Fig. 1. 



The weiglit A is a s<|uare plate of gun-metal, .suspended 

 by the spiral spring, L, which is attached, at the lower end. 

 to thf horizontal arm, K, projecting from the jilate, and, at 

 the upper end, to a sujiport connected with the frame. 

 Five steel rods, E, F, (>, H, I, maintain the heavy pliite 

 in a vertical position The ends of these rods are pointed, 

 and one end of each rests in a conical steel cup on the 

 plate and the othei' end in a similar cup on the frame. 

 The rods E, F and G compel the plate to move only in its 

 own plane, the rods H and I prevent it rotating or moving 



