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.
The hen, when permitted to follow her natural course, rises with the sun and goes to roost at sunset. During the winter months she puts in short days off the roost. It has been shown that an artificial day, made by piecing out daylight by means of artificial light, might keep the hen scratching and feeding longer, with an increased production of eggs as a result. Many experiments of this character have been carried out, and there appears to be a general conclusion that the use of artificial light for this purpose is profitable.
Experiments conducted recently by the agricultural department of a large university indicate that in poultry husbandry, when artificial light is applied to the right kind of stock with correct methods of feeding, the distribution of egg-production throughout the whole year can be radically changed. The supply of eggs may be increased in autumn and winter and decreased in spring and summer. Data on the amount of illumination have not been published, but it is said that the most satisfactory results have been obtained when the artificial illumination is used from sunset until about 9 P. M. throughout the year.
An increase of 30 to 40 per cent. in the number of eggs laid on a poultry-farm in England as the result of installing electric lamps in the hen-houses was reported in 1913. On this farm there were nearly 200 yards of hen-houses containing about 6000 hens, and the runs were lighted on dark mornings and early nights of the year preceding the report. About 300 small lamps varying from 8 to 32 candle-power were used in the houses. It was found that an imitation of sunset was necessary by switching off the 32 candle-power lamps at 6 P. M. and the 16 candle-power lamps at 9:30. This left only the 8 candle-power lamps burning, and in the faint illumination the hens sought the roosting-places. At 10 P. M. the remaining lights were extinguished. It was found that if all the lights were extinguished suddenly the fowls went to sleep on the ground and thus became a prey to parasites. The increase in production of eggs is brought about merely by keeping the fowls awake longer. On the same farm the growth of chicks incubated during the winter months increased by one third through the use of electric light which kept them feeding longer.
Many fishermen will testify that artificial light seems to attract fish, and various reports have been circulated regarding the efficacy of using artificial light for this purpose on a commercial scale. One report which bears the earmarks of authenticity is from Italy, where it is said that electric lights were successfully used as "bait" to augment the supply of fish during the war. The lamps were submerged to a considerable depth and the fish were attracted in such large numbers that the use of artificial light was profitable. The claims made were that the supply of fish was not only increased by night fishing but that a number of fishermen were thereby released for national service during the war. An interesting incident pertaining to fish, but perhaps not an important factor in production, is the use of electric lights in the summer over the reservoirs of a fish hatchery. These lights, which hang low, attract myriads of bugs, many of which fall in the water and furnish natural and inexpensive food for the fish.
Many experiments have been carried out in the forcing of plants by means of artificial light. Some of these were conducted forty years ago, when artificial light was more costly than at the present time. Of course, it is well known that light is essential to plant life and in general it is reasonable to believe that daylight is the most desirable quality of light for plants. In greenhouses the forcing of plants is desirable, owing to the restricted area for cultivation. It has been established that some of the ultra-violet rays which are absorbed or not transmitted by glass are harmful to growing plants. For this reason an arc-lamp designed for forcing purposes should be equipped with a glass globe. F. W. Rane reported in 1894 upon some experiments with electric carbon-filament lamps in greenhouses in which satisfactory results were obtained by using the artificial light several hours each night. Prof. L. H. Bailey also conducted experiments with the arc-lamp and concluded that there were beneficial results if the light was filtered through clear glass. Without considering the details of the experiment, we find some of Rane's conclusions of interest, especially when it is remembered that the carbon-filament lamps used at that time were of very low efficiency compared with the filament lamps at the present time. Some of his conclusions were as follows:
The incandescent electric light has a marked effect upon greenhouse plants.
The light appears to be beneficial to some plants grown for foliage, such as lettuce. The lettuce was earlier, weighed more and stood more erect.
Flowering plants blossomed earlier and continued to bloom longer under the light. The light influences some plants, such as spinach and endive, to quickly run to seed, which is objectionable in forcing these plants for sale.
The stronger the candle-power the more marked the results, other conditions being the same.
Most plants tended toward a taller growth under the light.
It is doubtful whether the incandescent light can be used in the greenhouse from a practical and economic standpoint on other plants than lettuce and perhaps flowering plants; and at present prices (1894) it is a question if it will pay to employ it even for these.
There are many points about the incandescent electric light that appear to make it preferable to the arc light for greenhouse use.
Although we have not yet thoroughly established the economy and practicability of the electric light upon plant growth, still I am convinced that there is a future in it.
These are encouraging conclusions, considering the fact that the cost of light from incandescent lamps at the present time is only a small fraction of its cost at that time.