New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1892-07-04
NOW TO MEASURE HUMIDITY.

Health md comfort temper and business success.
lie dryncss OF racctracLs and the result 81 many
wagcrs and scores Of other human Interests depend
., largely nj this time ~ year upon the number OF
grain, Of vntcrvapor suspended In each cubic foot
OF air that II Is strange that people do not study
that Invisible md abomlnable but potent and tangible
ncnd atmospheric humidity. Tho device whercwith
INF, nnv De accomplished Is the Mgrometcr. an In
,trumcnt Of which thcrc several varieties. and
supply Of which may 10 found In scores Of shops In
this CITY.
several hygrometcrs, Regnaults. Dariells. Baches
md others employ polished surface u glass or metal
art!lcallv cooled by Ice or chemicals 10 n point mt
which condensation ~ moisture from the mir as on
~. outside 81 an Ice pitcher Tho difference
In temperature between this surface ut the Instant II
becomes believed md the free air Is made The basis
81 computations for which one needs "A table Of
figures supplied by experts. instruments Of TINS
typo are suited to popular use 1t being difficult
matter 10 determine precisely the temperature NJ when
the dow begins TO form.
Another form If hvgromctcr Is made 81 two care
flllv selected thermometers one Of which has rs
Lulb covered with thin muslin and Is thus kept moist
from atte cup or tube ~ water. Evaporation coos
the bulb and the difference I'm the readings Of the two
Thermometers reveals the dcgce of satHrtion Of the
air MT that time and place. Slightly differing tables
Of l,rcs for the guidance Of those using the wet and
dry bulb hyrr0mccr have been prepared by the late
Mr. James Glashcr famous British metcorologlst and
aeronnut and By the United States Weather Bureau
This instrument has Its drawbacks. The observer
needs a table Of figures to interpret TIC readings. II
+ difficult 10 manage Il IN freezing weather. and the
divergence between the Indications Of the two thcr
momctcrs increases somewhat II there be much wind
Nevertheless the wct-and-drv bulb hgyromctcr is
tensively used not only by gardeners and physicians
but bv experts I'm obscrvatOrcs The official observa
lions Of humidity by The United States Weather
bureau arc made with IT, precautions being taken to
give ample ventilation but 10 shelter tho instrument
from strong breczes.
The essential principle IN another class q hvgrom
meters Is the swelling and shrinking which moIc less
moisture causes In many substances. Every one
knows for Instance. how bureau drawers ard closet
door, that are well behaved Mt Other times Of wear
stick fast when closed. vccxtionsv. under the
influence Of SIMMER mnglincSs Quills and other
materials arc utilized for measuring humidity. The
halr. however IS the favorltc reliance II manv OF
the best Instrument makers. Saussure was perhaps
the first 10 adopt II the fibre being hung pcrpen-
dicularly its upper end being fastened to a frame,
and the lower end dccacly weighted. being cocd
about the axcl Of q dial needle. The Hoppe hygrom-
ctcr extensively used in Continental Europe Is
only n modification Of this type. So. too. Is Lam
brccht's "Polymetcr.' another German device which
IS rapidly coming into use abroad and in the United
States. This instrument. when properly adjusted,
reads In rather close conformity With wetaDd-dry-
bulb hygrometer. and II has the great merit. for
popular use Of telling It's story nj once. like clock
or Thermometer, without reference u other data.
1t has q scale ranging from zero which stands fpr
absolute drvness. to 10 Wscn Slen I compielo
ago Of satuIaton relative humidity. Is greater OF
less the needle approaches one end or the other
as to The dew point md "vapor tension" Ineligible
at n glance for the use Of experts