d the production was increased in various operations from 30 per cent.
for the least increase to 100 per cent. for the greatest increase.
Inasmuch as the energy consumption in the latter case was increased
seven times and the illumination twenty-five times, it is seen that the
increase in intensity of illumination was due largely to the use of
proper reflectors and to the general layout of the new lighting-system.

In another case a 10 per cent. increase in production was obtained by
increasing the intensity of illumination from 3 foot-candles to about 12
foot-candles. This increase of four times in the intensity of
illumination involved an increase in consumption of electrical energy of
three times the original amount at an increase in cost equal to 1.2 per
cent. of the pay-roll. In another test an increase of 10 per cent. in
production was obtained at an increase in cost equal to less than 1 per
cent. of the payroll. The efficiency of well-designed lighting
installations is illustrated in this case, for the illumination
intensity was increased six times by doubling the consumption of
electrical energy.

Various other tests could be cited, but these would merely emphasize the
same results. However, it may be stated that the factory
superintendents involved are convinced that adequate and proper
artificial lighting is a great factor in increasing production. Mr. W. A.
Durgin, who conducted the tests, has stated that the average result of
increasing the intensity of illumination and of properly designing the
lighting installations in factories will be at least a 15 per cent.
increase in production at an increased cost of not more than 5 per cent.
of the pay-roll. This is apparently a conservative statement. When it is
considered that generally the cost of lighting is only a fraction of 1
per cent. of the cost of products to the consumer, it is seen that the
additional cost of obtaining an increase of 15 per cent. in production
is inappreciable.

Industrial superintendents are just beginning to see the advantage of
adequate artificial lighting, but the low standards of lighting which
were inaugurated when artificial light was much more costly than it is
to-day persist tenaciously. When high intensities of proper illumination
are once tried, they invariably prove successful in the industries. Not
only does the worker see all his operations better, but there appears to
be an enlivening effect upon individuals under the hi