114 
Sea Log and Sounding Machine . 
very plausible in theory, is found totally useless in prac- 
tice. Thus the friction on a rope long enough to extend 
beyond the eddy of the vessel’s wake would, in many cir- 
cumstances, on the old plan, totally impede the action of 
the rotator.* Under this impression, the friction in Mas- 
sey’s patent log is reduced to almost nothing by the follow- 
ing simple contrivance. The whole log, consisting of the 
register, a , connecting cord, c, and the rotator, ft, is com- 
mitted to the water, by a log line of sufficient length to 
reach beyond the eddy of the vessel’s wake. As the 
ship moves forwards, the rotator, and cord, c, between it 
and the register, revolve and set the wheels into motion ; 
nor has the roughest sea been found to prevent this ac- 
tion. 
The rotator also, in this log, is so constru cted as always 
to preserve a horizontal position, by being made nearly of 
the same specific gravity as water ; which is effected by 
means of an air tube passing through its centre : an indis- 
pensible requisite, which no former machine possessed ; 
and for the want of which, they could not preserve that 
horizontal position in fast and slow sailing, which is ab- 
solutely necessary to obtain any true result. 
Another very important improvement consists in the 
contrivance for regulating the rotator, by which means 
every rotator revolves once on its axis in passing the same 
space : as it was found utterly impossible to construct two 
rotators so exactly alike as stated by Smeaton, without 
means of adjustment. 
To sum up the properties of Massey’s patent log, in a 
few words it may be observed, 
* Smeaton, in the account of his experiments, in the work before quoted, ob- 
serves : “ During this run, I observed that the resistance of the water to the 
line and plate was very considerable, and increased the friction of the spindle so 
much, as to prevent it from beginning to turn, till the plate had twisted the line 
to such a degree, that when it did set a going it would frequently run one hun- 
dred and fifty or two hundred turns at once.’* 
