DESCRIPTION ET USAGE 
D'UN PENDULE A TRÉS-LONGUE PÉRIODE 
POUR LA MESURE DU ROULIS ABSOLU. 
Extrait d'une lettre de Mr W. FROUDE à Mr BERTIN. 
My dear Sir, 
DANONE I have succeeded in obtaining three most excel- 
lent trials at sea, with the two skips, which, as I think 
J informed you, the Admiralty has devoted to the experi- 
ment: — and, with greatly improved apparatus, in each 
of the ships, we obtained a continuous record of the rol- 
Eng for an hour without intermission, the two ships 
being kept very near to each other, in order that the 
waves to which they were exposed should be as nearly 
as possible the same. The two ships were very nearly 
auke in size and in form (14.100 english tons), but one of 
them had lateral keels, one on each side. 
