522 EEPOKT— 1888. 



sition could take place at ordinary tempei-atures by the application of 

 sufEcient pressure during a sufBciently long time. 



In a further communication, Van 't Hoff' mentions that at his 

 suggestion Spring bad subjected the double acetate to high pressures at 

 varying temperatures, and adds that by pi-olongiug at 16° the pressure 

 of 6,000 atmos. evidence of decomposition is readily recognisable. Van 't 

 Hoff points out that determinations of the minimum pressure required 

 to produce reactions of this kind, together with measurements of the 

 resulting changes of volume, will make it possible to express in 

 kilogram-metres the absorption of energj^ involved in the reaction, and 

 conversely the liberation of energy resulting from the reverse change. 



Report of the Committee, consisting of Sir F. J. Bramwell, IMr. 

 E. A. CowPER, Mr. Gr. J. Symons, Professors Gr. H. Darwin and 

 EwiNG, Mr. Isaac Roberts, Mr. Thomas G-ray, Dr. John Evans, 

 Professors Lebour, Prestwich, Hull, Meldola, and Judd, and 

 Mr. J. Glaisher, appointed for the pjurpose of considering the 

 advisability and possibility of establishing in other parts of 

 the country observations upon the prevalence of Earth Tremors 

 similar to those noiu being wiade in Durham,. 



During the past year a good deal has been done in the way of devising, 

 constructing, and testing new forms or modifications of old forms of 

 earth-tremor-registeriug instruments. Professor Milne in Japan and 

 Dr. Holden, of the Lick Observatoiy in California, have instituted sys- 

 tems of earthquake observations, the former employing instruments of 

 various kinds, chiefly of his own invention, and the latter using Professor 

 Swing's duplex seismograph. Professor Ewing has, however, recently 

 been engaged in materially improving this instrument and also in per- 

 fecting a cheaper time-recording apparatus with a special view to nume- 

 rous observers stationed in many parts of the country. He has also quite 

 recently brought out a new sensitive electric seismoscope. Mr. E. A. 

 Cowper has described at the present meeting of the Association yet 

 another seismoscope, of entirely new construction, specially adapted for 

 recording vertical motion. The North of England Institute of Mining- 

 and Mechanical Engineers have continued the series of observations on 

 the coast of Durham at Marsden, and have now three instruments at 

 work there, including a form of cheap recorder constructed from the 

 designs of Mr. M. Walton Brown. That institute has issued an elaborate 

 preliminary report on these instruments (1888). 



An important observing station, with adequate funds, promises to be 

 instituted by Mr. C. Davison and Professor Poynting at Birmingham. 



Considering that so much is being done with the object of securing 

 suitable forms of instruments, and that these investigations are still in- 

 complete in many ways, the Committee feel that it would be premature 

 for them to select and recommend any special recorder at present. They 

 wish, however, to emphasise the view that, whilst carefully finished, 

 highly sensitive, and necessarily expensive seismoscopes made to record 



' Ber. 20, R. 311, 1888 ; Rec. trav. cliim. 6, p. 137 ; C. S. J. Alt. 1888, p. 404. 



