Richmond dispatch. [volume] (Richmond, Va.) 1884-1903, 1898-06-12

i OF two forrnS--Ole in Wbicn d. he"'s -
is allowed TO swing by Its upper edse ~
| a position fronting the wind, the amoun1
| Of its deviation from tho verhcai peius
| measured. and the other Ia which the
plate Is supported by springs. the degree
! OF compression OF the springs being the
quantity registered In that case. Oh the
speed anemometers. the best-known io,n
~ the Robinson" In which four heHis-
pherical cups are carried at the eNI'e"'
ties Of couple OF cross-bars.
RAIN AND sUNCHINE
The chief remaining instruments are
those for measuring the amount of ram
fall and of full sunshine. The rain-gauSe
consists essentially OF a funnel TO coiee'
the rain. and a graduated glass 10
measure Il. The sunshine recorder usu-
allv consists of large glass globe ar
ranged TO throw an image OF the pun
on a piece of specially-prepared paper.
This image moves along the paper as
the sun moves IN the sky, charring IL as
Il moves, and at the end of the day IL 10
oasy 10 see, from the broken, burnt trace
at what hours the sun was SHINING cledi'
and when II was hidden by a cloud.
An amusing difficulty was encountered
In an ATTEMPT to set on foot another IN
auirv. The superintendent OF the Meteo-
rological Department at the time Wisheu
10 have a measure OF the rate at winch
eyaporation took place. and therefore e1-
nosed carefully quantities oA
water in the open air IN shallow vessel
For a few days the record seemed quite
satisfactory. Then the evaporation
showed a sudden increase, and developer
I'm the most erratic and inexpncapie man
ner. until it was found that some spar
rows had come 70 the conclusion that
tor "A
provision for their morning tuD' anu
had made use of IL accordingly.
A large proportion Of the meteorologi-
cal Instruments at Greenwich and other
| hrst-cless observatories are arranged 10
be self-recording. II was early felt that
II was necessary that the records OF the
| barometer and thermometer should De
| as nearly as possible continuous; ana al
one time, within the memory or the MEM
| bers of the staff still living, 1t was the
| duty OF the observer to read certain
| set of instruments at regular two-houl
intervals during the whole Of the day ano
| night-a work probably the most monoto'
nous, trying, and distasteful Of any tha'
the observatory had TO show.
The two-hour record was no doubt prac
tically equivalent TO a continuous one
but it entalled a heavy amount OF labor
|
troduced whenever they were available
| The earliest of these were mechanical
and several still make their records II
this manner.
on the roof of the octagon-room w
find besides the two turrets already re
ferred 10, a small wooden cabin pulIt o.
a platform several feet above the roo
level. This cabin and the Northwestern
turret contain the wind-registerlng III
struments. Opening the turret door, "
find ourselves In a tiny room Whlch
nearly filled by a small table. Opo
| this table lies "A graduated sheet OF pape
in a metal frame, and as we Iooh
, il we see that q clock set up close |
the table Is slowly drawing the pape
across it, Three little pencils rest hghti
on the face Of the paper at dliIeren
| points. One Of these, and usually III
most restless, il connected with spin
, | die which comes down into the tul
+ ret from the roof, and which is, IN rae
! | the spindle of the wind vane. Inc gear
| ing is 50 contrived that the mouoh
a pivot Of the vane Is turned INTO INC
: tion i'm O. straight line at right angles [
the direction in which the paper is draw
; bv the clock. A second pencil Is cor
nected with the wind pressure anemom'
= ter. The third pencil indicates IN
amount of rain that has fallen since IN
\ last setting. the pencil moved by hoa
! in the receiver of the rain gauge
4 REGISTRATION.
S An objection to all the mechanical me
! thods of continuous registration Is, ina
e however carefully the gearing betWee
, the instrument itself and the pencil
T contrived. however lightly the penc
moves over the paper, yet some trlctlo
enters In and affects the record; IN
S Is of no great moment in wind reglstr'
ton, when we are dealing win so po"e
G ful an agent as the vino, but u Decoh''
serious matter when the barometer
considered since it's variations requll
To be registered with the greatest minute
S ness When photography, therefore, Wa
invented. meteOrologists were vel
D prompt to take advantage OF tn
new ally. A beam of light pas
ing over the head OF the COLUMN
of mercury in Thermometer
> barometer could easily be made 10 Ia
! upon a drum revolving once IN the IWei
u ty-four hours, and covered win Sne'
of Photographic paper. In TINS cds'
= when the sensitive paper Is u0NeioPC'
!, we find its upper half blacKeheo' VI
u lower edge of the blackened part shown
l. an IRREGULAR curve according as the mel
> curry I'm the thermometer or baronete
+ rose or fell, ana admitted less OF nor
light through the space above IL
Here we have a perfect means OK rSsN
! trotion. the passage Of the Hght eNei
, rises no friction or check on the Ire
motion of the mercury in the tuoe' Oh
tha turning OF the cylinder covered .
the sensitive paper, whilst IL Is easy
= obtain a time scale on the register
y cutting off the light for an Instances
at each hour. In this way the wei an
dry bulb thermometers in the great she
- make their registers. 49,,
e The supply of material TO the Mete1
- J rolocical Office is not the only use Oh u
" | Greenwich meteorological oDseIVallo"
j Two elements of meteorology, the zen
perature and the pressure OF the dOiiiu'
nhere have the very directest peaIlt
I. mon astronomical work. And TINS 1T |"
Wsvs An instrument Is sensible 10 he'
!, and cold. and undergoes changes OF lott
= size or scale which, however, aosoiu'
- " minute, become, with the ihCrc"se
delicacv OF modern work. not merely al
oreciable but important. SO, 100, VII
7, the density of the atmosphere; the Asi
- from q distant star entering our dIiIio'
. nhere suffers refracton; and, being I'M
: bent out of its path, the star appear
- higher i'm the heavens than II reaHy J
- THO amount of the bending varies VII
= the density of the layers OF air lhroue
which the light has 10 pass. Inc |"
grcat meteorological instruments, II
=, Thermometer and the barometer ar
tnorstore astronomical instruments
l. well.
Conceit.
CpuCk.)