During the period elapsing- between the Louisiana Purchase 

 Exposition and the Panama-Pacific International Exposition, 

 wonderful advances had been made in the efficiencies of all 

 types of lighting units. This made it possible to illuminate in 

 the main group of buildings, approximately 8,000,000 sq. ft. 

 (743,200 sq. m.) of horizontal and vertical surfaces to an illumi- 

 nation ranging from 1/10 to 1/4 of a foot-candle in the inci- 

 .lental gardens and roadways, from 1/4 to 3 foot-candles in the 

 building facades and adjacent lawns and gardens, and from 5 to 

 15 foot-candles on the towers, flags and sculptural groups. The 

 lighting load on the main group of buildings, including the 

 window lighting and the scintillator, was approximately 5000 kw. 

 The total connected load for all purposes, including Zone, For- 

 eign and State sections and exhibitors, for light and power, was 

 13,954 kw.. with a maximum peak of 8200 kw. and an average 

 peak of 7880 kw\ During the Exposition period of approxi- 

 m.ately ten months, a total of 16,057,790 kw.-hr. was purchased 

 from the Pacific Gas and Electric Company. Of this amount, 

 5,582,906 kw.-hr. were sold to exhibitors and concessionaires, the 

 remaining 10,474,884 kw.-hr. being used by the Exposition. 



In order to obtain a harmonious illumination scheme, it was 

 necessary to visualize the lighting as a whole, and to establish 

 illumination and color values for every part of the Exposition 

 before definite specifications for lighting equipment could be 

 made. The preliminary tests and calculations on lighting units 

 that had been selected for use at the Exposition were made at 

 the Illuminating Engineering Laboratory. The lighting units 

 \YeTe all new developments, in many cases used in new ways. 

 This necessitated a vast amount of preliminary investigation 

 v/hich usually took the form of calculations of the illumination 

 on the grounds, facades and towers. Erom these calculated val- 

 ues it was possible to determine if the selected lighting units 

 were of the right size and were properly arranged on the pre- 

 liminary plans. As soon as any particular phase of the lighting 

 was fully decided upon, the illumination and luminous flux 

 values were calculated in all their minute details, so that long 

 before the Exposition opened there were on hand complete sets 

 of illumination diagrams for all the various courts, buildings and 

 towers. 



The principal features of the lighting are described under 

 their respective headings and illustrated by the accompanying 

 plates. 



LUMINOUS EFFECTS' IN TOWER ILLUMINATION. 

 — This illumination consisted in flood-lighting the towers with a 

 white rising light which created shadows. The shadows were in 

 turn illuminated by concealed colored light on the various stages, 

 thereby producing detail in shadow. This combination gave the 



