New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1873-08-23
SCIENCE AT PORTLAND.
Continues from First PAGE,

sIO1VCU,
new paper
MERIDLANAL ARCS MEASURED IN THE PROGRESS OF Tak
,Go AsI suRvEf-Br }. Z. HILGARD or WASHINGTON.
In the progress of the Coast Survey the figure of tat
portion OF the globe covered by its operations ia de-
termined necessary part OF the work The triangu-
atOn determines the lineal dimensions, the astronon-
spheroid The simplest form in which geodelc surveys
have been employed determine the figure OF the earth
OF latitude have formerly been susceptible Of far greater
precision than those OF longitude which measure arcs
the American chrongraphc method Of measuring lOng.
tude the accuracy is obtained IN the measure OF
the Coast Survey will serveto determine the figure of
that portion Of the globe IL covers Two me,
-one extending from Pennington. Me-. to Nantucket,
and the other from the head OF Chesapeake Bay 10
makes comparison in detail Of these with the
era degree of the earth described by Capt Clark OF the
nai arcs in different countres-aggregating
76o of the quadrant and arrives at the conclusion that
epticty of in 1885, with slightly increased equatorial
radius. The length of the quadrant is 1000 medires
system supposed represent This corresponds to
in the theoreo value OF the metere Oh loo Oh
Prof Peirce mentioned that the method OF triangula
ton in great survey by means Of 6 Ss 5rede
cessOr Prof Bache He explained IN ae,a tne b plo
StsnsvS rlspgusops with greater accuracy than
was before conceivable. The connections Delveen Tue
lines were selected we're explained, and the relation OF
these 10 final map making exemphed. He stated
thousand wears ago was more accurate than that
Gently mapped OF Western Territories He agreed
on ' 10 insure perfect accuracy ali the past surveys
will have to be repeated all over the world. The
Will have TO be adopted abroad from ours. and
the made for the purpose will he exported
Survey will thereby be so clearly demonstrated that
attempt will ever be made to tranmel its operations
AUTOMATIC REGISTERING AND PRINTING THERMoMETER-
BY PROP. C. W. HoUGH, DIRECTOR OF THE DUDLEY
OBSERVATORY.
mechansms have been constructed for recording auto
maticslly the fluctuations of temperature.
The machines heretofore used for TINS purpose may be
divided classes First when the record is made
by metallic thermometer mechanically, ny using
either single wire or combination OF rods having
different cOetcients OF expansion second tIe appnca-
ton of photography by of which the hight Of the
mercury in the thermometer tube is photographed IN
the form OF continuous curve thifd, records MADE AT
definite intervals from mercury thermometer ~ the
OF electr0ndg netism
The first method is capable OF giving approximate re-
suits are however serious objections 10 Its use
the most important OF which Is the i0Ssbility OF max
iug piece OF metal subjected 10 any wVlh hhnclih us
OF length. To Illustrate rod OF brass on eteel De
made support a weight, viz, 10 pounds and at the
same time be subjected 10 neat ana cOd lOI SNORT e,
the length OF the oar at given temperature VIII not DC
consequently. metallic thermometers will not maintain
fixed zero fact observed by many mete0rolOgsts. OF
the second method by means Of pAotography may De
only necessary 10 state that the amount OF attention re-
CURED IN the preparation OF the paper tue developing
the photograph and the measuring Of the records,
gsts. The records also are often indisnct and the
mons are lost The method however, is susceptible
of giving accurate results. OF the thrd form insru
means OF electrO-magnetsm the zero of the therm0n
eter If mercury, viii remain fixed and the records
will be correct within certain Discriminate limits The
only objection this form Of lies in the fact that
changes occurring between the intervals OF recording
are not shown. With this exception tn, method may
regarded for general superior to those before
mentioned. ,.,, - -. -. -
come the objections before urged, and 10 60 step
further by securing not only continuous curve but,
al definite intervals, results printed with type. one OF
the first things requisite i'll printing mechanism Is 70
secure a thermometer which shall keep liked zero,
otherwise the variable corrections necessary to be
applied, will ID great measure Vuale tne Naiue oi
results. Some four year, since mealIc hermOh-
eer consisting of brass and steel rods was constructed
TO which was attached the printing mechanism. but
owing to the continued change OF the zero was soon
soon after we constructed the meteorograph, which
was described at meeting in 1870 The labor demanded,
however the conversion OF curve III numerical re-
suts was 50 considerable FOR single year. That 1t
was thought advisable 10 construct printer
The thermometer which we have adopted consists or
glass tube bent in the of sphon, the closed leg
Of which is filled with alcohol and the open one with
end there rests an ivory suspended deete
balance having platinum Nv wiro cInnu Of mercurv
in the thermometer tuno rises OF falls. from the
effect OF temperaure the platinum wires dip in small
mercury cups placed underneath them thereby causing
a current Of electricity 10 pass through one OF TWO
eecromagnets operating mechanism for giving motion
no fine micrometer screw. The motion Of this screw
eevates lowers the balance thereby DieablhK tDe
circuit Whenever q change Of temperature equal TO
one-tenth of degree Fahrenheit occurs, the magnetic
circuit is completed, and the is moved space
equivalent The change In the night OF Tie mercury Ill
BY this method which is the in principle as our
printing barometer described at the meeting IN 1866 no
work is required be done by the thermometer with
the exception Of supporting one-haf the weight OF Inc
float the force required TO estaDIsh na9neuc cur
rent exceed two grains, and when once esta
nshed even this pressure ON the mercury column Is
removed. When the temperature rises or taIis tne
screw follows its notion at the same time the cock
work the type wheels indicating the temperature
which is printed at the end Of each hour on slip OF
paper moving in front OF them. pencil held against
revolving drum also records continuous curve, ex-
libiting al a glance the hight OF the thermometer.
This machine gives the temperature 10 tentns OF De
the probable error OF an impression being about
two-tenths of a degree OF Fahrenheit IHe ciOckwofK
and printing mechanism is placed inside the building
the Thermometer and carriage only beng outside Inc
connection between them is made by fine wire running
pues, and attached TO the mierometer screw
aud balance.
DESCENT OF RIVERS IN THE MISSISSIPPI yALLEY-BY
COL. CHARLES wHITTLEsY OF CLEVELAND, ONO.
For only Of the streams in this valley has the
observations are highly important for Typographical
ant rond the descent OF the channel is Approximately
uniform. Between points only 100 200 miles apart
II nearly proportional TO the distance, and the eeva
ton OF the adjacent country may be obtained with
barometer or by merely short side levels, using low
water base For instance the Mississippi at the
mouth of the ohiois 924 feet above the Gulf Midway
cannot be far from half that elevation, or l6l
feet. The paper then proceeds TO give the
elevations as' taken at different points , along along
The interesting line OF plane 1000 feet above tide
at the southwest on the Rio Grand, near
Analoo thence in along the base OF he rolling
or hill country turning up the Colorado thence 10 the
neighbOrhoOd Of Fort Worth the Trinity Ql0O, and
by another curvature TO the south and east around
into the Valley Of the Red River, up this
stream into the Indian country, distance
not vet determined doubling back the north side 10
the Valley OF the Arkansas. The Professor went on 10
trace this plain bringing around to the butressess OF
tbe Cumbera nds, near TuscumDia, and cutting
the tops OF the hills Lexington UP tue
Allegheny IL intesects the river hills at the
month Of French Creek. 100 feet above low
water marks 1t passes 435 feet above the surface OF
Lake Erie irtersecng the slopes Of IT'S south shore
near their IONS leaving below 1t large space IN New
York ana on the north of the lakes IN Canada In the
IOwer Peninsula Michigan there are very few points
that reach up ii, the highest pinnacle OF Mackha"
Island being 200 feet below.
THE EXISTENCE OF LIVE mAMMoTHs-BY PROF. fEUcHT