The Washington times., 1923-04-15

sistance may cause serious dim
ming Of the lamps. One per cent
drop in VOLTAGE. e., .06 volts on
a 6-volt system - will result in
about 4 per cent loss in candle.
power. Much larger losses than this
aften result from a dirty or oily
contact. The surest way of check
ing such losses Is by means Of q
voltmeter.
HeadIightfhg has been given con-
siderable study by engineers and es.
pecially by the committee on motor
vehicle lighting of the illuminate
ing Engineering Society. For safe
driving at reasonable speed, on an
unlighted road, tits obviously neces-
sary that the motorist be able to
project light on the road 100 to 200
feet in advance. The remarkable
development of refIectors. lenses,
and concentrated filament incandes-
cent lamps, has made it possible to
do this economically, so that only a
small amount of electric power is
required. The great difficulty has
been to direct the light where
wanted without subjecting other
users OF the highway to fntolerable
glare, and thus incur serious acct
dent hazard.
At first this, situation was met by
diInTning the headlights. This, how
ever, blinds the driver and incurs
for him as serious a, hazard as the
glare does for others. Moreover
with increasing travel, the more fire.
quent diInning becomes quite bur-
den. All sorts Of methods of i'm
proving this situation have been
tried out.
The best scheme SO far devised, is
to defect the light, usually by pris-
matte glass lenses. so as to illumi-
nate the roadway and prevent
enough light rising to the eye level
to cause serious glare. This ideal
is not thoroughly realized, since the
road surface is not flat and the car
in operation not always level How.
ever, the glazing condition is avoided
most OF the time. and the quick
flashes of, light usually encountered
are much less Objectionable than the
more sustained exposure under form.
er practices. In order to avoid too
great vertical dimension of beam,
II is necessary to focus the lamp
carefully in the reflector.
1t is desirable to have a beam wide
enough to illuminate the bitches or
other distractions at the edge of
the road, especially around slight
curvatures. Therefore, most of the
lenses have prisms designed ia
widen the beam. 1t Is possible to
produce. the spread by the use OF
specially designed reflectors, and the
light can be DETECTED by a slight
fitting of reflectors. However. tilt.
ing a parabolic reflector will not in
itself fully meet the situation. since
1t does not provide lateral spread.
About thirteen of the States, rep
resenting over half of the motor We.
hlcie registration of the United
States, have adopted regulations in
cooperating the principle of reflec-
ton and spread as outlined. These
regulations are based on the specffi-
cations prepared by the Illuminating
Engineering Society after an extend.
cd study of the problem in collabora-
ton with some of the State authori.
ties. representatives of the Society Of
Automotive Engineers and other in
terested organizations.
motorists have, with the exception
or Few careless or reckless drivers,
shown a real desire to comply with
the regulations. However, to make
the application practicable, two
equipment sold must be capable of
meeting the requirements in service.
and, second. motorists must keen
them In adjustment, especially on
renewing lamps.
In order to insure the former. it is
usually required that devices CASUALLY
lenses) be submitted for approval
Such equipment is subjected to
carefully specified laboratory test.
This has been of great benefit to all-
tomobilists in eliminating Door. and
to some extent, inefficient equipment
from the market.
To facilitate the matter of adjust.
ment, the manufacturer is required
to furnish purchasers with approved
instructions. In some States inspec-
ton stations have been established.
to which motorist can go and have
his headlights inspected and adjust
ed for prescribed nominal fee. It is,
however, important that motorists,
in general, be educated to the i'm
portance OF adjustment, because an
improperly adjusted lamp can undo
all the benefit of the best equipment.
II on a level road the beam shows
bright on a vehicle or building above
the level Of the headlights, or If
there are dark spots in the illumi-
mated area. 1t is an evidence Of the
need of adjustment. This is not a
difficult operation and can be easily
carried out in accordance with the
instructions prepared for the particu-
lar device. The increased comfort
and safety of driving with proper