of Edinburgh, Session 1885-86. 
683 
Monday, 19 th April 1886. 
Sir WILLIAM THOMSON, Hon. Vice-President, 
in the Chair. 
The President laid before the Society a proposal for a Subscription 
to present a Medal to Professor van Beneden on the occasion of his 
Jubilee as Professor. 
The President read a letter from the Committee of Organisation 
of the “ Congres International d’Hyclrologie et de Climatologie de 
Biarritz,” to be held at Biarritz on the 1st of: October of the present 
year. 
The President read a letter from the President of the Society of 
Antiquaries of London, calling the attention of the Society to a 
memorandum in reference to the preservation of the Court Bolls of 
the Manors of this country. 
The following Communications were read : — 
1. On a new form of Portable Spring Balance for the 
Measurement of Terrestrial Gravity. By Sir W. 
Thomson. 
The design and construction of the instrument now to be described 
was undertaken on the suggestion of General Walker, of the East 
Indian Trigonometrical Survey. At the Aberdeen Meeting of the 
British Association in 1885, General Walker obtained the appoint- 
ment of a committee to examine into the whole question of the 
present methods and instruments for the measurement of gravita- 
tional force, and to promote investigation, having for its object the 
production of gravitation measuring instruments of a more reliable 
and accurate character than those now in use. 
The secretary of this committee, Professor Poynting, has already 
issued a circular note to the members of the committee (of whom 
the author is one), stating the conditions which must be fulfilled by 
any gravimeter laid before the committee for examination and 
report. 
