454 FERREE AND RAND— LIGHTING 



were employed. These reflectors are of modern design and repre- 

 sent very well glassware of medium density. In case of the indirect 

 system corrugated mirror reflectors were used inclosed in brass 

 bowls. These reflectors are also of modern design and give effects 

 which may be taken to represent very well those obtained in good 

 indirect lighting. The tests were taken at four positions in the 

 room, one with six, one with four, one with two, and one with none 

 of the lighting units in the field of view. The last three of these 

 positions are marked with a cross in Fig. i, east elevation. A 

 graphic representation of the results of the tests for the four po- 

 sitions is given in Chart i. Because of the amount of space that it 

 would require, a tabular statement of results from which these and 

 subsequent charts were constructed will not be given in this paper. 

 In the second series of experiments we undertook to determine 

 the most favorable intensities of illumination for the three types of 

 installations we had used in the first series ; and in addition the 

 effect of varying the intensity of the illumination with the particu- 

 lar grouping of distribution factors represented in each case. The 

 tests were made in the same room, with the same fixtures, and in 

 general with the same conditions of installation and methods of 

 working as were described in the account of the experiments of the 

 first series. To secure the various degrees of intensity of light 

 needed, lamps of different wattages were employed. In order to 

 keep the distribution factors as nearly constant as possible for a 

 given type of system, the lamps used in making the tests for that 

 type of system were all of one wattage, i. c, were all 15's, 25's, 40's, 

 6o's, or lOo's. For the indirect and semi-indirect systems 25, 40, 

 60, and lOO-watt lamps were employed. Our fixtures for the direct 

 system were so installed that either one or two lamps could be used 

 in each fixture, totalling respectively 8 and 16. In order to get a 

 wider range of intensities both numbers of lamps were used, i. e., 

 one series of tests was made with 8 lamps, and another with 16. 

 Also four intensities of light were employed in each case. These 

 intensities were secured in the 8-lamp system by using lamps to- 

 talling 120, 365, 400 and 800 watts. In case of the semi-indirect 

 and indirect reflectors socket extenders had to be used with the 25 

 and 40-watt lamps. That is, without the extenders these lamps, 



