36 BEPORT— 1894. 



60^. The local societies were so distributed over the country that most 

 places where it was desirable that one of these instruments should be 

 placed were within the area of one of them. Instruments placed on the 

 course of great lines of fault (or dislocation of the strata) would yield 

 results of much value. 



Mr. Horace Darwin exhibited and explained the construction and use 

 of the bifilar pendulum. He said it was not affected by the rapid, com- 

 plicated movements which took place during an earthquake, or by the 

 slight tremors caused by passing carts or trains. The movements which 

 it would measure were such as would make a factory chimney or a 

 vertical post fixed in the ground lean over to one side. Extremely small 

 movements of this kind could be measured and recorded on photo- 

 graphically prepared paper. A full account of the instrument was given 

 in ' Nature,' July 12. It is made by the Cambridge Scientific Instrument 

 Company. 



Mr. Symons, as Chairman of the Earth-tremors Committee, explained 

 how the work of the Committee had grown and in what direction they 

 needed additional help. In the first place, the attention of the Committee 

 had been directed to a solution of the question why certain vibrations 

 were recorded by an instrument which had been placed at the bottom of 

 one of the deep coal-mines of the district of Newcastle-on-Tyne. Instead 

 of a straight line a series of pulsations had been obtained. They were 

 traced to two causes — one the gradual settlement of the ground in conse- 

 quence of the removal of the coal, the other the beating of the waves on 

 the coast. They had since been looking for traces of earthquake tremors, 

 Mr. Davison, on one occasion, watched his instrument for some time, as he 

 found pulsations were taking place. These pulsations eventually turned) 

 out to have been produced by the earthquake then going on in Greece, 

 They wanted information as to the changes going on in connection with 

 the faults in geological strata, and, if possible, to get records of the altera- 

 tions in the earth's crust caused by tidal waves. When the ocean was 

 piled up at one part of the earth's surface it was quite possible that the 

 elastic surface of the earth bent slightly under it. Observations of that' 

 kind should be made at more than one station. The work was now- 

 going on at Birmingham under Mr. Davison, but they hoped that the 

 Association would give them a grant for a second instrument. Thev 

 wished to make sui-e that they were recording, not merely local phenomena, 

 but the great general phenomena of the earth's crust. He was glad to be 

 able to record that one instrument had been established at an observatory 

 .south of Biarritz by M. Antoine d'Abbadie, who had kindly presentee? 

 a duplicate instrument to the new observatory at Edinburgh. They were 

 anxious to see two or three instruments of this kind established in different 

 parts of the British Isles, and hoped that some of the wealthy friends of 

 the societies represented at that Conference might co-operate in findin ti- 

 the money for the instruments. 



Mr. Tiddeman asked whether the instrument could be placed in an 

 ordinary house, or whether it required a special place in a separate- 

 building. 



Mr, Symons replied that Mr. Davison had placed it on the cellar floor. 

 A separate building might be preferable, but was more expensive. 



Mr. INIills did not think the instrument would be of mnch use to 

 person .^1 without a special knowledge of it. 



