184 REPORT — 1895. 



UarHt. Tremors. — Fifth Report of ih.e Committee, consistin/i of Mr G. 

 J. Symons, Mr. C. Davison {Secretary), Sir F J. Bramwell, Pro- 

 fessor G. H. Darwix, Professor J. A. Ewixg, Dr. Isaac Roberts, 

 Mr. Thomas Gray, Sir Johx Evans, Professors J. Prestwich, 

 E. Hull, G. A. Lebour, R. Meldola, and J. W. Jcdd, Mr. M. 

 Walton Brown, Mr. J. Glaisher, Professor C. G. Knott, Pro- 

 fessor J. H. PoYNTiNG, Mr. Horace Darwin, ruiri Dr. R. Copeland, 

 appointed for the Investi(jatioii of Earth Tremors in this Country. 

 (Droiun up by the Secretary.) 



ArrEXDIX. — Kbfe on the liUtory of the Horizontal and Bijilar Pcndidinnn. 



/yy C. Davison'. ' pa,/c 184 



Since tlieir last Report was presented, the Committee have purchased 

 two bifilar pendulums from the Cambridge Scientific Instrument Com- 

 pany. Tiiese instruments are similar in most respects to tlie pendulum 

 with which experiments were made in 1893 (Report, 1893, pp. 291-303), 

 but several improvements have been introduced in order to correct one or 

 two defects which those experiments brought to light. The changes made 

 are described in the Report of 1894 (pp. 145-146, 158-160), and a 

 'detailed account of the new instrument is given in ' Nature,' vol. 1., 

 1894, pp. 246-249. Each pendulum is provided with a photographic 

 recording apparatus. One of them has been erected on the old foundation 

 in the cellar of the Secretary's house at Birmingham, l)ut at too recent a 

 date to allow atiy results to be included in this Report. It was intended 

 that the second instrument should be placed in a building about three- 

 quarters of a mile to the east of the fii'st, but it was afterwards found 

 that the construction of the foundation might endanger the stability of 

 the walls. Arrangements are accordingly being made for the erection of 

 this instrument on another site in the neighbourhood of the former, and 

 it is hoped that a comparison of the records of both may lie completed 

 before the next meeting of the Association. The second pendulum will 

 then be available for use elsewhere. 



The Committee recommend that they be reappointed, with the addi- 

 tion of ]\Ir. G. F. Deacon. 



APPENDIX. 



JVote on fho History of the Horizontal and Jiifilar Pendulums. 



By C. Davison. 



In previous Reports of this Committee, as well as in those of the 

 Committee on the Lunar Disturbance of Gravity (1881-82), reference is 

 made to the history of the horizontal and bifilar pendulums. A recent 

 work by Mr. Claudius Kennedy ' contains an interesting chapter on this 

 subject, and gives some additional facts which it seems desirable to 

 eiubodv in this note. 



' A Fen- Chapters in Astronomy (London, 1894), pp. 93-103. 



