amount of light. The walls of the court, so far as they show, should
be made as white as possible.
A modification of light court is suggested in
Fig. F, in which the light court is of uniform length, but in the lower
half of the elevation its width decreases successively at each floor.
Where the ends of the light court are not needed for illumination, this
modification saves considerable space for office purposes, and still
gives the same amount of light. The sizes of the canopies are found by
the same rule as is given above, but they are set out into the light
court so that they form a sort of terrace, and the floor itself is carried
out, thus adding to the available office space. The illustration shows
the proper arrangement of the court where the width of the upper part is
three-tenths the height of the whole court, and where the length is not
more than two or three times the width of the court. If the length of
the court is more than three times the width, then in order to get the
same illumination on the several floors, we need a new rule, which is as
follows: Measure the distance from the top of each canopy to the top of
the light court, find the sum of these numbers; each of these numbers
bears the same relation to this sum as the projection of the corresponding
canopy bears to half the width of the light court at the top. Between
the two extreme cases, viz. the square and the rectangle having one side
three times the other, the sizes of the canopies can be determined with
sufficient accuracy by interpolating between the sizes given by the two
rules.
In stores it is generally possible to do away
with light shafts by installing prisms either in the front or in the
front and rear, according to the size. In case of illumination from
both ends of the store, all stairways and elevators should be located,
if possible, in the middle of the store. Where it is desirable to employ
a light shaft to illuminate the central portion of a long store, the
modification show above of the light court can be used to considerable
advantage. The light shaft should be set with its longest dimension at
right angles to the length of the store, and occupy nearly the full width
of the store. Whenever prisms are installed in the windows of light
shafts which are covered over with skylight glass the skylight glass
should have a polished surface
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