steamships and by all sailing ships whether on the
port or starboard tack, and whether
close-hauled or not, unless the circumstances of the
case are such as to render a departure from the
rule necessary, in order to avoid immediate
danger, and subject also to the proviso that due
regard shall be had to the dangers of navigation,
and, as regards sailing ships on the starboard
tack close-hauled, to the keeping such ships
under command."

The law is now read, even in public inquiries,
as if that passage which we have bracketed
were not contained in it. Assuredly, it is quite
obvious that this rule is of immense value, and
will tend only to prevent collision, if it be
obeyed only when it is meant to be obeyed,
that is to say, when there is risk, and that not
instant risk, of a collision by the close passing
of ships if they continue their respective courses.
Practically, the fact is that only one ship's
officer in a thousand can tell when if he holds
his course, and if the approaching ship shall do
the same, there being no risk of collision, there
is no need to port the helm. Moreover, the one
man in a thousand cannot calculate upon the
other vessel's course being maintained, upon her
not porting her helm because it is not necessary.
This being the case, the custom is for a man to
make sure that he shall be, in case of misfortune,
found at least on the safe side of the law.
It would go hard, if collision occurred, with the
master of a vessel who had not ported his helm.
And so it happens, that because captains do not
act upon the first condition of the law in knowing
when their course is safe, they very often,
in their doubt and dread of being found
offenders against the rule of the road, port their
helm when by so doing they can only run into
each other's way. There can be shown at least
one case in which immediately before the stroke
of ruin order has been given on board the vessel
being run down to port the helm, when by
so doing she was actually turned to meet the
full shock of a collision at a time when an
opposite order would have turned her tail aside,
and, by a very close shave, enabled her to slip
out of danger.

It was the consideration of this, says Mr.
Perry, that set him upon the devising of his
Dial. Three consecutive cases of collision on
the coast of Australia, those of the Lady Bird
and Champion, of the White Swan and Burra
Burra, and of the Storm Bird and Queen, proved
to be cases in which the ships would have been
perfectly safe as they were— in one case not
crossing each other's paths at all, in the two
other cases one crossing a mile or two behind
the other— but in which terrible disaster was
run into by porting the helm in obedience to
half only of the letter of the law. It was
especially by these three accidents that Mr. Perry's
wits were set to work. It was worthy of
remark that not only had the officers of these six
ships altered their courses because they were
ignorant of their safely, but after they had
altered they maintained them because they were
ignorant of their danger, ignorant although the
lights were rapidly approaching and when
collision became imminent. In each case, it is
said, the Dial would at once have told them
what it, on the peril of their lives, behoved
them all to know.

Perry's Dial— it is to be known by the
tremendous name of "Patent Anti-Collision Dial
and Shipwreck Preventor"— is simply an instrument
that saves calculation. The author's
private and pet name for it is "Elucidating
Trigonometrical Formula." Of such instruments
it is said sometimes that they save science
and tend to beget ignorant and rash reliance on
machinery instead of wit. But, although there
is no problem in nautical astronomy easier than
the finding of the latitude, we can't succeed in
it exactly without help of the quadrant; we use
the sextant as a measuring instrument when we
desire to find the exact longitude. The ship's
compass measures exactly the angle of her head
with the magnetic meridian. Then why not add
to these an exact measure of the relation of the
ship's course to that of a vessel nearing her.

Again, the most scientific of masters does not
stay on deck all night. The watch in which
the chance of collision is greatest, usually falls
to one of his mates, and upon another vessel's
light appearing, the immediate knowledge of
her course, and action upon that
knowledge within five or ten minutes, is what is
required for perfect safety. But even supposing
the captain to be an Admirable Crichton, it is by
no means every mate who would rouse him up
whenever there appeared a speck of light on the
horizon.

The use of the dial consists in an adjustment
that does not occupy a minute, made immediately
after sighting a ship's light, and a second, equally
quick, observation made after a short interval of
time. The length of time that will elapse
between the seeing of the lights and the ships'
meeting, will depend, of course, upon the power
of the light itself, upon the joint speed of the
two ships, and upon the angle at which they
approach each other.

The lights used by British sailing vessels
and steamers are prescribed by law. They are a
white light at the masthead, visible— the limit
is of their power, but they are powerful enough—
at a distance of six or seven miles, and coloured
side lights— red on the port side, green on the
starboard side— visible three miles off. Foreign
vessels, when in British waters, generally use
these lights; but elsewhere their mark is a single
white light at the bowsprit end, visible five or
six miles off.

Then as to the joint speed. We will suppose
that two swift steamers are approaching each
other in a straight line, at a joint speed of
twenty-four knots. They would take fifteen
minutes to meet from a distance of six miles.
The whole results attainable by use of the dial
could be assured in five minutes, and the
proper precautions, therefore, could be taken
while the steamers were still four miles apart.
In the case of foreign ships, with the bowsprit
light visible, say only five miles off (which