Sea Log and Sounding Machine . lid 
1. It will give tlie true distance sailed, from steerage 
way, to any velocity with which the swiftest sailing ves- 
sel can move. 
&. It not only gives more accurately than the common 
log the rate of sailing, hut the actual space sailed through 
since the last inspection. 
3. It is attended with less trouble than the common 
log, and no mistakes can possibly arise from the result it 
gives. 
It remains to point out one great and desirable advan- 
tage, which may very reasonably be expected to result 
from the use of this log, and that is, a more complete 
knowledge of the currents in various parts of the ocean, 
which has hitherto been very imperfectly attained ; as it 
was not possible to know, with any certainty, whether the 
wide difference found between the real distance, and that 
given by the common log, was caused by the known im- 
perfections of that method of reckoning, or by the opera- 
tion of currents. 
Dr. Maskelyne, in the same work just quoted, further 
observes : “There is another argument which adds much 
strength to the foregoing ones, and greatly enforces a 
uniform and correct length of the logline, on board all 
ships ; that in many parts of the ocean, especially be= 
tween the tropics, and near most head-lands, there are 
considerable cu^gents, which must introduce a fresh er- 
ror into the reckoning ; and if this error should happen 
to combine with that already produced by a wrong length 
of the logline, as it may as well as not, it is not easy to 
say how far the total error of the reckoning might go, 
or to what inconveniences or dangers the ship might be 
exposed on that account. But if the just and proper 
length of the logline were used on board of ail ships, 
they would be then liable only to the errors of the cur- 
rents themselves ; and even these, as far as they are con- 
