187 
The principle upon which the apparatus works is so simple 
that it hardly requires explanation. At the beginning of 
the .operation the weight of the tube is wholly supported by 
the water; by drawing off the water the support is very gently 
removed and the weight thrown upon the fibre. The 
relation between the actual weight put upon the fibre and 
the weight of water drawn off will vary for every different 
dimension of the containing vessel and floating cylinder, but 
in regularly shaped vessels it will always be in the direct 
ratio of the sectional areas of the floating vessel and the 
difference between this and the sectional area of the contain- 
ing vessel, i.e. t in cylindrical vessels the sectional area of the 
ring of water surrounding the floating cylinder. 
