16 
BRITISH ASSOCIATION.— 1835 . 
so as to absorb all pulses of sound, would be best adapted for this 
purpose. 
All superfluous space should be excluded. 
The air should be maintained as uniformly equal as possible. 
All concave surfaces ought to be avoided; foci, in such cases, 
collecting the sound at one point, while in other places it is compa¬ 
ratively deficient. 
Dr. Reid, after alluding to the peculiarities in the construction of 
his class-room, and to many other buildings, adverted to a number 
of circumstances connected with the roof, walls, and floor of different 
buildings, the introduction of ornaments, the variety of form that 
might be adopted according as the walls, roof, &c. were made to 
reflect or absorb sounds, and the different conditions to be attended 
to where the speaker was confined to one spot, and where indivi¬ 
duals rose in every place to address an assembly. 
Experimental Researches into the Laws of the Motion of Floating 
Bodies . By J. S. Russell. 
It was the object of these inquiries to assist in bringing to per¬ 
fection the theory of Hydrodynamics, and ascertain the causes of 
certain anomalous facts in the resistance of fluids, so as to reduce 
them under the dominion of known laws. 
The resistance of fluids to the motion of floating vessels is found 
in practice to differ widely from theory, being, in certain cases, 
double or triple of what theory gives, and in other and higher 
velocities, much less. These deviations have now been ascertained 
to follow two simple and very beautiful laws : 1st, A law giving a 
certain emersion of the body from the fluid as a function of the ve¬ 
locity. 2nd, A law giving the resistance of the fluid as a function 
of the velocity and magnitude of a wave propagated through the 
fluid, according to the law of Lagrange. These two laws compre¬ 
hend the anomalous facts, and lead to the following 
Results . 
1. That the resistance of a fluid to the motion of a floating body 
will rapidly increase as the velocity of the body rises towards the 
velocity of the wave, and will become greatest when they approach 
nearest to equality. 
2. That when the velocity of the body is rendered greater than 
that due to the wave, the motion of the body is greatly facilitated: 
it remains poised on the summit of the wave in a position which 
may be one of stable equilibrium ; and this effect is such that at a 
velocity of 9 miles an hour the resistance is less than at a velocity 
of 6 miles behind the wave. 
- 3. The velocity of the wave is independent of the breadth of the 
fluid and varies with the square root of the depth . 
