ii& Sect Log and Sounding Machine, 
revolution when the distance sailed is one hundred miles . 
When the machine is to be used, all the fingers of the in- 
dices are set to 0, and both register and rotator commit- 
ted to the water. 
As the vessel moves forward, the log must follow’, and 
from the obliquity of the vanes it is evident the rotator, b ? 
must revolve quicker or slower, correspondent to the 
ship’s velocity. This rotatory motion is communicated 
by the cord c to the universal joint d, connected with the 
wheels, which consequently revolve with the rotator and 
cord, and thus the actual space passed through, in any 
given time, is registered on the indices. 
Every occasional or momentary acceleration or retar- 
dation of the vessel, from irregularity of wind, or other 
causes, which are either altogether passed over, or very 
vaguely guessed at, in general, are accurately registered 
on this machine, which not only gives the actual rate of 
sailing, but the actual distance sailed, since the last in- 
spection. 
A very little reflection will convince any observer of 
the great superiority of this machine over all others which 
have been hitherto introduced. 
It may appear rather presumptuous to criticise the la- 
bours of Smeaton, and many others, whose endeavours 
were not crowned with complete success : but it is neces- 
sary to point out where their plans failed, in order to prove 
. the very superior advantages of Massey’s log ; for though 
some of the machines answered their purposes tolerably 
well under certain circumstances, none of them were near- 
ly correct under all circumstances. Some were erroneous 
when the ship moved less than four miles in the hour, and 
others became so when the rate was increased. * 
In most of the former inventions, the first mover was a 
spiral, or a rotator in the shape of a Y, and was generally 
attached to a register kept in the ship ; and as it was ab~ 
