ON THE DETERMINATION OF GRAVITY AT SEA. 511) 



APPENDIX I. 



The Determination of Gravity at Sea. — Report of the Commit tre, 

 consistinfi of Professor A. E. Love {Chairman), Professor 

 W. G. DuFFiELD {Secrctari/),Mv. T. W, Ciiaundy, and Professors 

 A. S. Eddington and H. H. Turner. 



[Plates VII.-XVIII.] 



Report upon the Comparison of the Aneroid and Mcreiinj Barometers. 

 Dvaivn up by the Secretary. 



1. Preliminary. 



In 1866^ attention was drawn to the possibility of employing au aneroid in 

 conjunction with a mercury barometer for the measurement of gravity 

 at certain land stations, but the variability of the elastic properties of the 

 metal boxes constituted a difficulty to its successful application. As it 

 was the opinion of meteorologists that aneroids had been greatly improved 

 in material and in construction, I took advantage of a generous offer from 

 the Cambridge Scientific Instrument Company to provide an aneroid 

 wherewith to test the method anew, this time at sea, during the voyage of 

 the British Association to and from Australia in 1914. 



It had scarcely been hoped that the investigation would lead at the 

 first attemjit to the successful determination of gravity at sea, but it was 

 hoped to gain experience and information which might serve to disclose 

 any defects which might be caj^able of subsequent remedy. On account 

 of the exigencies of war-time, the report has been condensed and the bulk 

 of the tables omitted. The original report is filed at the offices of the 

 British Association, where it may be consulted by those closely interested in 

 the subject. It sets forth the present state of science with regard to the 

 aneroid method of measuring the intensity of gravity over the oceans, and 

 the primary object in compiling it has been to place in the hands of future 

 investigators a record of the experience already gained. 



The results, which are discussed with some reserve in sections 8, 

 9 and 10, have, however, an interest of their own, and future work 

 will be eagerly awaited to see if the fall in the value of gravity between 

 Australia and India is real, or due to a systematic error to which the 

 aneroid is liable, or to some other uncorrected vagary of this instrument. 



In future experiments fuller acquaintance with the lag and the pump- 

 ing of the aneroid barometer for long periods previous and subsequent to 

 the voyage should solve the question whether Helmert's fornmla holds 

 good or not over the deep oceans. At present the indication, though not 

 the conclusion, is that it does not, gravity being apparently less over the 

 deep ocean than overland areas ; over inland seas, on the other hand, the 

 normal value may be exceeded. 



' Vou Wiillcrstoi'f Urbair, zycitec/iri/'< der oskrrcichischen O'cacllscluift fiir Mctcvro- 

 logie, Band I, I8G(.>. 



