1881.] 



Major J. Herschel. On Grauimeters. 



317 



agitation of a soap-film. A glass tube, blown into a shape somewhat 

 resembling a tobacco-pipe, had its month closed by such a film, while 

 its open stem was connected with a sounding flask. I did not succeed 

 in producing any visible agitation. When the film was uniformly 

 illuminated, or when it had become thin enough to produce iridescent 

 colours, on holding a high-pitched tuning-fork near the open end of 

 the stem, the whole surface of the film was immediately covered with 

 concentric rings, having the centre of the film for their centre. This 

 belongs to the class of effects so vividly described by Mr. Sedley 

 Taylor. A fork of the pitch of the sounding gas produced no visible 

 effect upon the film. 



January 20, 1881. 



THE PRESIDENT in the Chair. 



The Presents received were laid on the table, and thanks ordered for 

 them. 



The following Papers were read : — 



I. " On Gravimeters, with special reference to the Torsion- 

 Gravimeter designed by the late J. Allan Broun, F.R.S." 

 By Major J. Herschel, R.E., F.R.S., Deputy-Superintendent 

 of the Great Trigonometrical Survey of India. Received 

 October 31, 1880. 



(Abstract.) 



In the course of 1878-9 some correspondence passed between 

 Major- General Walker, the Surveyor-General of India, and the late 

 Mr. Broun, on the subject of an instrument designed by the latter, the 

 fate of which General Walker was desirous of learning. Interrupted 

 by the death of Mr. Broun, General Walker requested the Director- 

 General of Stores for India to inquire if the instrument could be pro- 

 cured for the Indian Government. It had meanwhile become the 

 property of the Royal Society. In order to comply with the Surveyor- 

 General's intention, the loan of the instrument was then obtained 

 from this Society, and it was placed in the hands of the author of this 

 paper to examine and report upon. 



The paper consists mainly of a narrative account of the examina- 

 tion, and the conclusions to which he has been led regarding instru- 

 ments of this class. 



