HoW It WorkS
A barometer measures changes in atmospheric pressure, which you can think of as the weight of the air above you.
Changes in atmospheric pressure at any given point typically foretell changes in the weather. Weather watchers there-
fore note a barometer’s reading, then observe how much and how fast the reading rises or falls. Rising pressure sig-
nals improving weather, while falling pressure portends deteriorating weather. Generally, a barometer works best when
mounted indoors where air pressure is the same as that outside, but the instrument is less subject to the elements.
The Chelsea barometer is an aneroid barometer. This means it measures atmospheric pressure mechanically, without
Mercury or other fluids. Instead it uses a vacuum and a hollow metallic diaphragm. Pressure changes on the diaphragm
cause the black indicator hand on the dial to move. You can manually position the stationary gold hand over the black
indicator hand, and return later to note how much the pressure has changed and whether it is rising or falling.
Barometers can measure atmospheric pressure in inches, millibars, or centimeters. At sea level, normal atmospheric pres-
sure is approximately 29.92 inches, 1014 millibars, or 76 centimeters. At higher elevations, the average pressure will be less
because there is less air pressure overhead. Normal weather variations cause the pressure to rise or fall an inch or less
so you may see little movement of the black hand for several days at a time. A passing storm often brings rapidly falling
pressure.
SEttInG For local altItudE
When a Chelsea barometer leaves our factory it is adjusted to register pressure at sea level, which is the standard way to
measure barometric pressure regardless of location or altitude. Since atmospheric pressure decreases as altitude increas-
es, if you are in a higher altitude location it will be necessary for you to adjust the barometer to give you a reading cor-
rected to sea level. To do this, call the local weather bureau and ask for the present barometer reading. Then adjust the
barometer’s black indicator hand to the reading given. This can be accomplished by turning the small screw on the back
of the barometer case. If you are at an altitude of 5,000 feet or greater, the barometer should be adjusted professionally.
carInG For tHE caSE
Chelsea Clock cases are constructed of exceptionally high quality brass, highly polished to a fine finish, and then care-
fully lacquered for long-lasting protection. The chemicals in fingerprints and even ordinary dust may eventually mar
this finish. Therefore, we suggest cleaning the case weekly with a clean soft cloth. Do
not
use polish, cleaner, or other
liquids that could tarnish or pit the finish. Treated with this care, the lacquer coating will not be broken and the clock
case should retain its bright appearance for many years.
SErVIcInG tHE clock or BaroMEtEr
Under normal operating conditions, the clock should be cleaned, oiled, and adjusted about every five to seven years.
Conditions such as extreme heat, cold, dust, and even idleness can adversely affect lubricating oils and therefore neces-
sitate more frequent servicing. A Chelsea clock or barometer is a precision instrument that should only be serviced by
our master clockmakers. When the clock or barometer requires cleaning or service, we urge you return it to our factory
repair center where an experienced master clockmaker will insure careful, efficient, and guaranteed work. Please take
extra care to double-box the clock to avoid damage in transit. You can find further packing and shipping advice online at
www.chelseaclock.com.
t h e B a ro m e te r
lIMItEd Warranty
A new Chelsea Ship’s Bell clock or barometer is warranted against defects in material and workmanship for five (5)
years from the date of original purchase. In the event of any such defect, please return the instrument postage prepaid,
along with an explanation of the defect to the address set forth below and it will be repaired or replaced, at our option
and our expense. Any defect or damage caused by misuse, accident, tampering or negligence of the user is not covered
by this warranty. Be certain to carefully and securely pack the instrument for return. We will not be responsible for dam-
age in shipment. The repaired or replacement instrument will be returned to you postage prepaid. All implied warranties
covering merchantability, fitness for particular purpose, or otherwise are limited in duration to five (5) years from the
date of original purchase. The repair or replacement of any defect is the exclusive remedy under this warranty. In addi-
tion, the warrantor shall not, under any circumstances, be liable or responsible hereunder for consequential, incidental,
indirect or special damages. Please note that some states do not allow limitations on how long an implied warranty lasts,
or the exclusion or limitation of incidental or consequential damages, so the foregoing limitation or exclusion may not
apply to you. This warranty gives you specific legal rights; you may also have other rights that vary from state to state.
Two Hundred Eighty Four Everett Avenue, Chelsea, Massachusetts 02150-1515 | Tel 617 884-0250 | chelseaclock.com
