Identifier: brynmawrcollegem1112bryn (find matches)
Title: Bryn Mawr College monographs
Year: 1901 (1900s)
Authors: Bryn Mawr College
Subjects:
Publisher: Bryn Mawr, Pa. : (The College)
Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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e distribution of light to thperimeter arm. This housing is made of black japanned irojand is painted a mat black on the inside, in order that, anearly as possible, all the light which passes to the perimetearm shall radiate directly from the lamp filament. Itdimensions are 4^4 by 43^ by 5 inches. A rectangular aperture 2y^ inches wide was cut out of the side of the housin;facing the perimeter arm, at the bottom, and for 3 incheback on the two adjacent sides. The relation of the lamp \\this aperture is such that the light radiates freely withoushadows from the filament to every point on the perimetearm. In order that the lamp may be removed when desiredthe bottom of the housing is hinged at the back and is hel(in place by a latch on either side. To prevent overheatiiijthe housing is well ventilated by specially designed lighttight ventilators—four in the sloping roof of the lamp housand four on each of the sides at the bottom. Provisions are made in the construction of the lamp-hous
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CO Ferree a*nd Rand : The Campperimeter. 5 for filtering the light to daylight quality. A well-seasonedtype C Mazda lamp, operated by ammeter and rheostatcontrol, is used as the source of light. The instrument isdesigned to run on any 110-volt circuit. In order that thelamp-cord which connects the lamp with the line shall bewell out of the road and shall not interfere with the rotationof the perimeter arm, it passes up through the hollow stemwhich supports the perimeter arm to two copper brushesfastened to a small hard-rubber base 2^ by ^ inches atthe top of the stem. These brushes are in contact with twocircular, insulated metal strips on the back of the brass disc tothe face of which is fastened the perimeter arm. From thesestrips the circuit is continued to the lamp by two insulatedwires which thread in and out of the short braces whichreenforce the lamp arm. This perimeter is not difficult to construct or to operate.It provides for a uniform illumination of the perimeter armin all

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