The southern press. [volume] (Washington [D.C.]) 1850-1852, 1851-03-04


have been introduced afer suhjaesing the results
obtained by former ones to discussion by the mod
ern methods Of analysis, and proving thus the ne
cessity for the change. BY the instruments now
used the attitudes Of places can be determined with
greater precision than that to which the places OF
the small stuTs given in the catalogues, and Il
~ now necessary TO resort 70 direct observations
for their places. The methods Of observations of
aximuth and the computations have been greatly
improved. Irregular attraction Of the plumb line
has been found in places where il has hitherto not
been supposed to exist, and the remedy for the
irregularities in local attractions, latitude and
azimuth has been applied.
Differences of longitude have been determined
by the electro magnetic telegraph between the sta
tons at Cambridge, New York, Philadelphia,
Washington, and Charleston; and also between
Washington and Cincinnati, as step in the chain
between Washington and New Orleans. This is
the first public work in which this method has
been used, and the first Of any kind in which it
has been perfected.
iude of point in the survey with European OBJ
servations have been made, first by the use Of the
chronometers of the Cunard steamers, and when
the limit Of accuracy thus attanable. had been
reached, by the transportation Of chronometers,
specially prepared for the purpose, between Cam
bridge and Liverpool. Astronomical observations
have been collected from various sources for the
modern methods.
A new base apparatus has keen devised by the
superintendent and constructed under his direc-
ton, by which the accuracy of such measurement
is increased and the time required for them dmn-
shed 1t is arranged so as to be of invarable
length at all temperatures, and when the temper
ature is rising and falling. 81
The Typographical system Of Lehman has been
introduced into the survey, and modified SO as to
adapt it to representing the slopes Of our coast.
Scales Of shade depending upon it have been in
troduced into the field work, and the drawing re-
duced in the Office.
improvements have been introduced into the
mode of observing currents, and of reducing and
representing the observations The recent meth
DDS of tidal reductions have been introduced upon
the work.
The Gulf stream has been explored from Hat
teras northward to the parallel of Cape Cod, by
instruments devised for ascertaining temperatures
below the surface where the accidental effects of
winds are not felt. The division of the Gulf
stream into two branches has been discovered by
the use Of these Instruments, and the "cold wall
limiting the stream inshore has been traced. The
law of decrease of temperature below the surface
has been developed by the same methods.
The sgeodetic formula and tables introduced
have been founded on careful mathematical anal
yss and on the most recent determinations of the
figure of the earth.
New plans for reducing drawings, for system in
engraving, for copying engraved maps by the
electrotype process for printing have been intro
duced.
A classification Of the specimens of the bottom
Of the has been made, with results interest
ing TO navigation and TO science.
Tidal observations have been collected at each
Of the principal ports that have been surveyed,
and provision has been made for their continu-
ance.
The remarkable phenomena Of the single day
sides in the Gulf Of Mexico have been developed,
to that practical tables may be given for the places
at which the observations have been made.
The progressive character of the work will APP
pear from the least consideration Of this list and
the necessity of retaining its connection with the
science of the country order that this character
may be preserved.
II, 1t is frequently urged that the changes on
our coast will IN time render the photography OF
the coast survey obsolete, and require new sur
veys. If SO, they can be made AT comparatively
small expense by the land determinations Of the
present survey. But the allegation is not true in
a general sense, but, the contrary, in the pro-
gress Of the coast survey, the parts of the coasts
which are changing, and those who are perma-
nent, become distinguished from each other. Thus
no change OF any Importance IN the channels en-
tering New York harbor or Delaware Bay has
taken place since the surveys of 1886 and lS43,
| although such changes have been alleged, and re-
| examinations have been made to determine the
| facts Davs's south shoal, south of Nantucket,
has undergone no material change since its discov-
| cry in 1916, though the contrary of this fact has
been stated; aud we might suppose, priori, that
considerable changes NJ sior Intervals, would oc-
| cur in such locality 1t ic indeed, more than
probable that Gedney channel, discovered by the
coast survey in 1885, was actually in existence
when Eas Barres' map made In 1850, and
the French fleet, under d 'Esta.ng, anchored off
the entrance in llIs Had i then been known,
New York city would have been rescued from the
occupation of the enemy, and the occurrences Of a
long train of disasters in revolutionary srug-
giles would have been prevented.
10. The chief of the photographic party is re-
sponsible for the due execution of the scientific d.
rections which he receives, and which can ema-
nate from no one so well as the general superin-
tendent of the work, who sees all the parts ar
ranges all the complex operations so that they
will fit together sptiy, watches their progress by
the monthly reports Of the assistants, and is thus
enabled to ensure the proportonate progress of
every part of the survey. The tendency, In a
WORK executed by many different individuals, is
the want of connection in methods and operations.
Each one sees only his own part of the work, con
sders it essential, and those of others of less I'M
portance The naty which is entirely and abso-
lutely necessary to success in such operations is
secured by superintendent, which, knowing the
wants Of each part Of the work, causes 1t to adj
vance as one operation. If the direction OF the
topography were disconnected from the triangu-
laiion, confusion would be produced, and the to-
pographer would bs obliged to determine over
again the points executed by the trIangulator.
! The difficulties which now and then occur, under
even we-regula,ed system, in finding the points
and marks left by the preceding party, who, IN
| tent on their own work, sometimes think too lit
tie of those who to follow them, would become
| the rule instead of the exception. The hydrog-
! raphy would in like manner suffer, not as now by
incidental careessness, or the wanton removal OF
signal but necessarily and generally; and II
would be found at last, as IN the British surveys,
| that they must determine second time their shore
| line and points of reference on the land. The
loss of time and additional expense thus involved
can be hardly foreseen. The differences, too,
would bs charged by each on the other as errors,
and there being no authority to appeal to for a
verifcation, all confidence would soon be lost in
1 the determinations. The work would inevitably
require to be done second time under proper
system.
1t is very certain that il the work is done now
/ by any but the most complete and perfect methods
it will hereafter be done over by such methods
and the expense now incurred and the time occu-
pied, will be thrown away.
| n, = the of the