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floor surfaces illuminated by parallel beams of light at various angles. It should be understood, of course, that in all these cases light is not confined to these surfaces, since it is always more or less strongly diffused over a much larger space. These diagrams are only intended to show the relative amount of illumination.
Fig. 69 is a cross-section of the newer form of saw-tooth roof construction, and illustrates the largely increased amount of surface lighted up by this method, which is now generally regarded as the best method of lighting up large areas in one-story shops. In this system of lighting the windows should face towards the north.
The width of the windows and their distance apart is a matter of great difference of opinion. Where the construction is of steel or wood they may be placed less than two feet apart, if it seems necessary to do this. Where brick walls are used the distance should generally be more, depending, of course, on the entire height of the wall.
Fig. 69. — Lighting Diagram. The Saw-tooth Construction of Roof.
In our arrangement of the windows in the machine shop (as given in Chapter II) the size is 4 feet wide and 10 feet high. These figures are the dimensions of the inside of the sashes, therefore providing 40 square feet of glass. This will make the opening in the wall nearly 5 feet wide, which, with bays of 18 feet 3 inches centers, two windows to each bay, will give about 4 feet 2 inches of brickwork between the windows. This will give sufficient
strength to the side walls, and will also provide quite enough light for all ordinary classes of machine shop work to be done in such a building.
In reference to the details of construction of the windows of machine shops and factory buildings, Mr. Edwy E. Benedict, of Waterbury, Conn., a successful designer of factory buildings, has adopted the plan of having in each window three sashes, each containing two lights of glass. In the case illustrated they are of 24 X 24 glass, making a window of 4 x 6 feet, as shown in front elevation in Fig. 70. An outside elevation of the upper portion is shown in Fig. 71; a horizontal section of one jamb, with sash, glass, weather strips, etc., in Fig. 72; an inside elevation, showing the inside finish at the top and bottom, in Fig. 73; and a vertical cross-section in Fig. 74.
Fig. 70.– Outside Elevation
Outside Elevation of upper portion. Some of the good features of this plan will, no doubt, be heartily commended by practical men. For instance, in Fig. 71 it will be noticed that the flat arch on the outside face of the wall reaches down below the segment, or supporting arch, which is shown in dotted lines in this figure, and drawn in full lines in Fig. 73. The vertical section in Fig. 78 shows its office, of making the top of the window weather-tight. It will also be noticed, by reference to Fig. 72, that the side face casings are built into the brick wall for the same purpose. These points, with the use of the Tabor weather strips, make a perfectly weather-tight arrangement that will be greatly appreciated by the
workmen in the shop, as well as the man who pays the coal bills. The working details are quite clearly shown in the several views.
Windows may be made of any desired height by increasing the length of the lights of glass. Thus, 24 x 36 glass would make a window 4 by 9 feet.
The bottom sash is glazed with clear glass, and the two above it with ribbed glass, the ribs running horizontal in all cases.
Skylights should not be used where they can be avoided, as they are a prolific source of leaky roofs,
Fig. 72. — Horizontal Section of damage by accidental breakage, as well as numer
Window jamb, sash, glass, etc. ous other difficulties, and even a light fall of snow quite destroys their lighting properties.
A translucent material formed on a fine wire netting is an excellent substitute for glass where skylights must be used. It gives a soft, diffused light and there is no danger of breakage as with glass. Windows in the ventilating portion of the roof are not only useful for lighting the central portion of the shop, but they conveniently act as ventilators when the sashes are hung on pivots and handled by cords. They may easily be so constructed as to avoid any trouble from leaking.
As to the kind of glass to be used, the plain glass is, of course, the cheapest. It must, however, be shaded by curtains, which can be readily run up and down; and these are liable to get out of order and to require a continual expense to keep them in presentable and useful condition. The amount thus spent added to the cost of plain glass will soon pay for good ground glass which will need no curtains, and which, while rendering the light soft and agreeable to the eyes of the workmen, will also diffuse it over the area of the shop much better and more
equally than the plain glass. At the same time Fig. 73. — Inside Elevation, showing none of the light is lost by interposed shades or
curtains. As to “stippled” glass, the stipple is apt to crack and peal off, and will also absorb considerable dirt and grease, making it much more difficult to
keep clean than clear or ground glass; and the repeated washings are apt to remove portions of the “stippling," leaving a patched and unsightly effect. The rough or “cathedral” glass is more expensive, not as agreeable to the eyes, and considerably lessens the volume of light. Windows of glass rods do not seem to have been sufficiently employed to demonstrate their usefulness. Ribbed glass is now quite popular for shop windows and diffuses a soft and agreeable light, and seems best adapted for the purpose.
We have seen shops in which practically the whole side wall was a mass of glass, only the space for the posts supporting the roof and the frames containing the sashes being opaque. Such a prodigality of light does not seem necessary in practice, and in fact it may be hurtful to the eyesight of the workmen, while the cost of construction and the continual cost of renewals and repairs of such a great quantity of glass will be a large initial expense as well as an important annual outlay. The expense of heating will also be largely increased.
Let us now consider the question of artificial light. First, the usual time during which we must provide for artificially lighting up the buildings. Omitting the six usual holidays of the year and calculating on the basis of a ten-hour day, we have 3,060 working hours in a year's work. If the working day begins at 7 A. M. and ends at 6 P. M., with one hour for dinner, we shall need artificial light, for the ordinarily well-lighted shops, for about 460 hours out of the entire 3,060 working hours of the year.
This will include “lighting-up time” divided among the different months as follows: January, 102 hours; February, 60 hours; March, 32 hours; May, 8 hours; June and July, none; August, 8 hours; September, 20 hours; October, 50 hours; November, 78 hours; and December, 102 hours.
To properly provide for sufficient lighting during these periods we must select some one of the many sys
tems in use, and the one which seems best adapted to Fig. 74. — Vertical
the conditions of the case. Whatever may be the future
development, either as to perfecting and simplifying its application, extending its sphere of usefulness, or reducing its cost, electricity at present stands at the head, when the question of a perfect light, or at least the most available one, is considered, for the illumination of nearly
all classes of large buildings, particularly such as are used for manufacturing purposes.
Still there seem to be indications that there may be yet other systems of artificial lighting which by development may become dangerous rivals of the popular systems of electric lighting - acetylene gas, for instance. This method is still in the infancy of its development and use, and there seem very few of the usual difficulties to be overcome excepting the danger of its explosion in the hands of inexperienced persons. This difficulty will probably be overcome in time and the use of it be as safe, both to generate and to manage, as electricity
It is also true that the system of electric lighting has many fatal accidents charged against it. These may all have been due to improperly constructed apparatus, the careless management of it, or the imperfect knowledge of its properties and action. The same may be said of acetylene gas.
That we have yet attained to the perfect artificial light no one will have the courage to assert, since improvements are continually in progress in this direction, but at present we must be satisfied with electricity, with gas as a supplementary light when the electric current is not available.
To provide an ample, proper, safe, and thorough system of illumination for buildings in which a large number of persons are obliged to labor for so many hours each year by its aid, would seem to be a matter that need not be argued or advocated. Yet there are many shops at the present time so constructed that some kind of an artificial light is needed all through the day, and in some at nearly all seasons of the year, and this condition prevails over a considerable part of the working space.
The result must necessarily be that both the quantity and the quality of the work done is below the standard, while the health and the eyesight of the employees are both unnecessarily impaired, since sunlight and fresh air are two very important elements necessary to the health, activity, and usefulness of the human family. Ofttimes the evil results from a lack of consideration or appreciation of these necessities, and sometimes perhaps from a false idea of economy on the part of those having charge of such matters, which has led them to provide very indifferent substitutes for sunlight, or, in its absence, a proper artificial light.
For it is true, “and pity 'tis, 'tis true,” that in some shops, even in this enlightened age, many hours' work is done by the smoky glimmer of dirty oil lamps, these relics of a bygone age, since they are not many steps in advance of the vessels of oil with their fibrous wicks resting against one side, used in the days of Abraham, 1920 B.C.
Although the common use of petroleum oils in various degrees of refining have revolutionized the old-time lamp, and the simplifying of the processes for