The Sun.
London, England, 1829-12-07 00:00:00

Captain, and .invalided home; Commander Smith,
of the Aritehne, to be Captain of the Magnificent..
APPOlNTMES'rg.—Lletitenant N. Shortlaud, to
the Arachne ; Lieutenant G. O. M'Donald to the
Childers ; Dr. Robert Lyon Harrower, Ast,igtAnt,"
Surgeon, to the St. Vincent, vice Mr. James- Lawr:F;
removed to Bermuda Hospital.
lieutenant Silver, of the Royal Hospital at Has-
lar, is promoted to the rank of retired eern-mtmder.
After so long a servitude, none have enjoyed a
higher degree
.ofrespect than that which follows
this individual in retirement from all who knsrw him.

Thti Countess of Harcourt transport arrived yes-
terday.
The Navy Board is at present at Plymouth su-
perintending some alteration in the details of the
Pock-yard there. Within these few days it has
been determined forthwith to abolish the Cheque
Offices in the different dock-yards, the mustering
duty of which is transferred to the Master Attend-
ant's Offiee,•and the money transactions to the
Nary Pay Office. A portion of the, detail of tl.e
Cheque Office will fall under the more immediate
cognizanee of the several Commissioners of the
Yards. The gentlemen who till the situations of
Clerks of the Cheque will be transferred to other
appointments.

A sloop of war of 18 guns, to be called the
Electra, ha's been laid down this week at the Dock-
yard at this pout. The frame for this vessel. (which
is to be built on the lines of the Ores•es) was or-
dered to be prepared when.hisaoyal Highness the
Duke of Clarence was in ollice.—Hampshirc
Tele-
graph.

ACCELERATION OF THE MAILS.

(From the Scotsman.)

At present we mean to confine our attention to I
one branch of this subject—the shortening of
the routes by which the mails travel from Lon-
don to Scotland—in reference to which we have
been furnished by ,a scientific friend with some
valuable materials, not accessible to ordinary
readers, and upon the accuracy of which perfect
reliance may be placed.
In all questions respecting a saving of length
in roads it is extremely desirable to know the
true spherical distance between their extremities,
or the shortest possible line from the one point
to the other, supposing the surface of the coun-
try to be as open and uniform as that of the sea.
This is important, not only as shewing the ex-
treme limit to which improvement may continu-
ally approximate, but it is of much positive and
practical value, as affording an infallible standard
by which the advantages of any single route as
to length may be estimated. If a road, for in-
stance, is marked out between Edinburgh and
Ayr, the question whether a different line should
be sought, may depend on the opinion formed,
whether the distance lost by windings is two
miles or six. How is this to be determined ?
The best maps are indifferent guides in such
matters, .and two surveyors, judging by the eye
merely, might form opinions as wide asunder as
those we have mentioned. It is only by means
of accurate determinations of the positions ,of
places, from geodesical and astronomical data,
that we can -arrive at a satisfactory solution of
such questions. Astronomical observations alone
do not give rigorously accurate results, because
in different countries the length of the degree is
found to have different values, which are not re-
ducible to any fixed rule ; and it is upon this
element that the conversion of the angular dis-
tances of the astronomer into ordinary measure
depends.
The first element in this calculation, is the
latitude and longitude of the several places ; and
to obtain these correctly, recourse has been had
to the Trigonometrical Survey, except for Edin-
burgh and Glasgow, the geographical position of
which has been derived from that of their Obser-
vatories. The table below may therefore be
received as good authority, and every care has
been taken to keep it free from errors of the
press.