Flo. 48. — Relative cost of i^rodudns a Riven nmount of
light by various illutiunuBtji at tuual pricoe. Costs
lire bajN^ od the following prices: Candles, 12 cents a
pound; kcrow^net 15 cents a gallon; eaa. $1 for 1000
cubic fc«t; electricity 10 cents a kilowutt hour, Tho
soUd linca represent coat of fufl or of eurrent, the
shaded parts the cost of the mantlea and bull^M*. Where
prices are different from thoao gi%'cn above* costs will
be correapoDdingly different.
The total economic gain which is made possible by doubling
the efficiency of produrtion of light is almost incalculable. To
consider only one item, it has l^een estimated by gwjd author-
ities that the liberal use of the newer lamps might reduce the
yearly consumption of coal in the United States by $8,000,()0(X
The general tendency has been, however, not to reduce the
amount of powder used, but rather to use more light. The abil-
ity to produce so much more hght without increasing the eost
has encouraged the development of methods of lighting in
which attention is given primarily to artistic appearance and
• U. S. Bur, Standards, Circ. 55.
HEAT AND LIGHT
205
to the comfort of the user rather than to getting m much light
as possible out of a fixture.
The cost of Ugh ting by any method depends to some extent
on local conditions^ and the statements of cost given below will
apply only approximately in any particular case. The cost
will naturally depend on the candle power of lamps used and
the time the lamps liurn. In order to make comparisons bcv
twec^o difTerent kinds of lamps, it is convenient to consider a
definite amount of lightin|ij, which is obtainetl by multiplying
the candle power of tlie lamps burnefl by the number of horn's
they Inirn. For exaniple, 1,000 candle-hours of lighting may
be obtained by lairning a 10-eaodle lamp 100 hours or a 50-
candle lamp 20 hours, Init if the lamps are of the same kind
the cost will l)e about the same. Calculations of the cost of
producing 1,000 candle-hours by different lamps arc sometimes
useful in choosing between lamps, but of coui*se it does not
necessarily follow that the lamp for which this cost is lowest is
most economical for household use.
I
I
Methods of distrifniHng light
The three methods of lighting, direct, indirect, and semP
indirect, are dei>endent for their efficiency on the type of shade
or reflector eniployed. By means of reflectors, light may be
concentrated on a small spot or spread out over a large area.
In the direct method of lighting, the light falls or is rcflectetl
directly on the objects to be lighted. Although the maximum
amount of light is furnished by this method, the disadvantages
of a fight that is too brilfiant and concejitrated are now recog-
niKed. If a drop light is used for close work, it is advisable at
the same time to have another light for the general illumina-
tion of the room in order to prevent a strain on the eyes pro-
duced l)y the contrast of a small briifiantly lighted area in a
practically dark room.
In indirect lighting all the light is reflected upward by an
opaque reflector and returned to the room diffused generally
from the ceiling. This metho^i is the most comfortable for the
eyes, but the most expensive.
4
I
I
^
206
A MANUAL OF HOME'-MAKING
Page 108
Presented as published in 1919. Historical recipes may not meet modern food-safety standards. Cook from the modern interpretation, not the original instructions.
AI-modernized reading of the original text
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Flo. 48. — Relative cost of i^rodudns a Riven nmount of
light by various illutiunuBtji at tuual pricoe. Costs
lire bajN^ od the following prices: Candles, 12 cents a
pound; kcrow^net 15 cents a gallon; eaa. $1 for 1000
cubic fc«t; electricity 10 cents a kilowutt hour, Tho
soUd linca represent coat of fufl or of eurrent, the
shaded parts the cost of the mantlea and bull^M*. Where
prices are different from thoao gi%'cn above* costs will
be correapoDdingly different.
The total economic gain which is made possible by doubling
the efficiency of produrtion of light is almost incalculable. To
consider only one item, it has l^een estimated by gwjd author-
ities that the liberal use of the newer lamps might reduce the
yearly consumption of coal in the United States by $8,000,()0(X
The general tendency has been, however, not to reduce the
amount of powder used, but rather to use more light. The abil-
ity to produce so much more hght without increasing the eost
has encouraged the development of methods of lighting in
which attention is given primarily to artistic appearance and
• U. S. Bur, Standards, Circ. 55.
HEAT AND LIGHT
205
to the comfort of the user rather than to getting m much light
as possible out of a fixture.
The cost of Ugh ting by any method depends to some extent
on local conditions^ and the statements of cost given below will
apply only approximately in any particular case. The cost
will naturally depend on the candle power of lamps used and
the time the lamps liurn. In order to make comparisons bcv
twec^o difTerent kinds of lamps, it is convenient to consider a
definite amount of lightin|ij, which is obtainetl by multiplying
the candle power of tlie lamps burnefl by the number of horn's
they Inirn. For exaniple, 1,000 candle-hours of lighting may
be obtained by lairning a 10-eaodle lamp 100 hours or a 50-
candle lamp 20 hours, Init if the lamps are of the same kind
the cost will l)e about the same. Calculations of the cost of
producing 1,000 candle-hours by different lamps arc sometimes
useful in choosing between lamps, but of coui*se it does not
necessarily follow that the lamp for which this cost is lowest is
most economical for household use.
I
I
Methods of distrifniHng light
The three methods of lighting, direct, indirect, and semP
indirect, are dei>endent for their efficiency on the type of shade
or reflector eniployed. By means of reflectors, light may be
concentrated on a small spot or spread out over a large area.
In the direct method of lighting, the light falls or is rcflectetl
directly on the objects to be lighted. Although the maximum
amount of light is furnished by this method, the disadvantages
of a fight that is too brilfiant and concejitrated are now recog-
niKed. If a drop light is used for close work, it is advisable at
the same time to have another light for the general illumina-
tion of the room in order to prevent a strain on the eyes pro-
duced l)y the contrast of a small briifiantly lighted area in a
practically dark room.
In indirect lighting all the light is reflected upward by an
opaque reflector and returned to the room diffused generally
from the ceiling. This metho^i is the most comfortable for the
eyes, but the most expensive.
4
I
I
^
206
A MANUAL OF HOME'-MAKING