40 



REPORT — 1901. 



of a coherer in air, and in different fluid or solid dielectrics. Thi'ough 

 interference- tubes with two branches only those vibrations are transmitted 

 which are parallel to the plane of the branches, and of a wave-length 

 equal to 1'6 the diameter of the tube. Such an interference-tube repre- 

 sents for electric waves a Nicol prism or a coloured glass plate for optical 

 waves. Wave-length or velocity inside the interference-tubes is about 

 -J of the wave-length or velocity outside in the free air. The ratio of the 

 wave-length in air and in fluids gives \/k, k being the specific inductive 

 capacity of the fluid. 



Seismological Investir/aUons. — Sixth Report of the Gommittee, consistinr/ 

 of Professor J. W. Judd {Chairman), Mr. J. MiLNE (Secretary), 

 Lord Kelvin, Professor T. G. Bonney, Mr. C. V. Boys, Professor 

 G. H. Darwin, Mr. Horace Darwin, Major L. Darwin, Professor 

 J. A. EwiNG, Professor C. G. Knott, Professor R. Meldola, Mr. 

 R. D. Oldham, Professor J. Perry, Mr. W. E. Plummer, Pro- 

 fessor J. H. Poynting, Mr. Clement Reid, Mr. Nelson Richard- 

 son, and Professor H. H. Turner. 



Contents. 



TAGS 



. 40 

 . 41 



II. 



I. On, Seismological Stations aJ/road and in Great Uritain 



Aiialyses of Recoo-ds for the Year I'^OO 



On the Approximate Frequency of Earthqualtes at different Stations. 



By J. Milne 41 



Experiments upon Piers 43* 



On the Comparison of Earth qualte Begisters from Kew, Skide, Bidston, and 

 Edinburgh. By J. Milne 44 



III. Oil the Records obtained from two similar Seismographs at Kew. By 



Dr. Chables Cheee 51 



IV. Movements of Horizontal Pendulums in relation, to Barometric Pressure. 



By J. MiLNB 52 



V. An Attempt to Measure Earth Movements at Ridgcway Fault. By Horace 



Dahwin 52 



I. On Seismological Stations abroad and in Great Britain. 



Seismographs of the type recommended by the Seismological Investiga- 

 tion Committee of the British Association have been constructed for and 

 in most instances are already established at the following stations : — 

 *I. 



*2 



Africa. 

 Australia 



4. 



.•5. 

 *6. 

 *7. 



Canada 



Cape Town. 

 Cairo. 

 Melbourne. 

 Sydney. 



Western Australia. 

 Toronto. 

 Victoria, B.C. 

 Colombo. 



Shide, Isle of Wight. 

 Kew. 

 Bidston. 

 Strassburg. 

 Hawaii. 

 Calcutta. 



Madras, Kodaikanal. 

 ,, Jugga Row. 

 Bombay. 

 Batavia. 

 Tokio. 



