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 higher intensities of illumination.  Mankind chooses a dimly lighted room in which to rest and to dream.  A room intensely lighted by means of well-designed units which are not glaring is comfortable but not conducive to quiet contemplation.  It is a place in which to be active.  This is perhaps one of the factors which makes for increased production under adequate lighting.

Civilization has just passed the threshold of the age of adequate artificial lighting and only a small percentage of the industries have increased their lighting standards commensurately to the possibilities of the present time.  If high-intensity artificial lighting was installed in all the industries and a 15 per cent. increase in production resulted, as tests appear to indicate, the increased production would be equal to that of nearly two million workers.  This great increase in output is brought about by lighting at an insignificant increase in cost but without the additional consumption of food or clothing.  Besides this increase in production there is the decrease in spoilage.  The saving possible in this respect through adequate lighting has been estimated for the industries of this country at $100,000,000.  If mankind is to have conveniences and luxuries, efficiency in production must be practised to the utmost and in the foregoing a proved means has been discussed.

There are many other ways in which artificial light may serve in increasing production.  Man has found that eight hours of sleep is sufficient to keep him fit for work if he has a sufficient amount of recreation.  Before the advent of artificial light the activities of the primitive savage were halted by darkness.  This may have been Nature’s intention, but civilized man has adapted himself to the changed conditions brought about by efficient and adequate artificial light.  There appears to be no fundamental reason for not imposing an artificial day upon plants, animals, chemical processes, etc.; and, in fact, experiments are being prosecuted in these directions.