Threatened exploitation of Pima Indians

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Index To Contents Page 269

PUBLISHED BY H. C. GUSHING, JR., 8 WEST 4OTH ST., NEW YORK, U.S.A,

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Copyright, 1922

by

H. C. GUSHING, JR.

Table Of Contents

Page

ILLUMINATION FUNDAMENTALS— PART 1 5

Amount of Light — Diffusion of Light — Color Quality of Illumination — Shadow — Uniformity of Illumination — Illumination of Vertical Surfaces — Desirable Wall Brightness — Maintenance.

Part I Illumination Fundamei^als

In the last year of the war and in the year immediately following, more progress was made in the application of artificial lighting than in any ten-year period preceding. Continual improvements in lamps and reflecting equipments, the constantly increasing availability of electric service, and the growing knowledge of illumination fundamentals, had, over a period of years, been paving the way for a sudden, sharp advance in lighting practice.

In no field of lighting was the progress so remarkable as in industry, for here the value of good illumination could be most easily measured in terms of dollars and cents. Tests conducted under actual working conditions demonstrated that startling increases in production were possible when antiquated lighting systems were replaced with new ones which produced lighting comparable with the daylight lighting of well designed modern factories. Most executives believed in good lighting, they acknowledged its importance, but what they did not know, and what had not been satisfactorily demonstrated, was that what were then considered good lighting installations we're not supplying enough light; in other' words, were not good lighting. Once the traditional illumination levels were broken through and levels 3, 4, and 5 times as high tried out in service, the handicap imposed by previous standards became apparent. Artificial lighting in every field moved forward.

Amount of Light

We do not know today how much light is right for the many applications. We do know that 3 or 4 foot-candles will enable one to see more detail than will 1 foot-candle; that 10 foot-candles will reveal more than 3 or 4; that 50 foot-candles will increase perception over 10; that 100, or even more, will sometimes produce still further improvements when the eyes are taxed to the utmost. We know that vision is quickened when the illumination is increased from 2 or 3 foot-candles to 10, 50, or to 100 or more. We know that persons with defective vision, and this means a surprisingly large proportion of the people, are even more greatly handicapped by poor lighting than are those with good vision, and that they respond more markedly to improvement in the lighting. Again we know that bright and cheerful surroundings are stimulating, that they inspire cleanliness, that they make for order and neatness. In these simple fundamental facts we find the' reasons why, in industry, higher levels of illumination increase production without imposing strain upon the employees, why they automatically reduce accident hazard, decrease spoilage, and improve morale; why, in the office, they enable more work to be performed with fewer headaches, less mistakes, and better tempers; why, in the store, they attract customers, facilitate the examination of material, and make for quicker sales; and why, in the home, they facilitate reading, working or studying at night.

Diffusion of Light

With the 10 to 1 increase in efficiency of the incandescent lamp, since its invention scarcely two-score years ago, has come the generation of large volumes of light in a small space. This means, of course, light sources of great brilliancy. A bright source does not in itself insure adequate lighting, in fact, unless skillfully handled, it presents a positive menace to vision. Objects are seen by the light which comes from them to the eye; light which comes directly from the light source to the eye or is reflected from the source to the eye by some polished surface is not only useless in illuminating the object viewed but if of high intensity or of large volume, it produces a blinding effect which seriously interferes with seeing and may result in permanent injury to the eyes. "Glare" is the term applied to light which obstructs vision in this way.

Glare blinds the driver of an automobile when approaching another with improperly adjusted headlights at night; it handicaps the workman who is trying to see fine details with a brilliai:: light source near his line of vision; it produces acute discomfort in the conference room where men sit facing inadequately shaded windows for a long period of time ; it is annoying in the home where wall brackets containing unshielded lamps are seen against dark backgrounds ; it blinds the ball player, who tries to follow the ball against the sun. In hundreds of ways it is constantly interfering with vision and handicapping us in work and play.

Specular reflection, that is, the reflections of light sources in polished surfaces, while sometimes an aid to vision, is often, because of its insidious nature, more harmful than direct glare. Under proper control, it facilitates the reading of the micrometer scale or the inspection of a polished surface; in excess, it becomes reflected glare, dulls perception, and paves the way for accident. As moderate specular reflection, it brings out the texture of materials and assists the housewife in her sewing; as reflected glare, it blurs the printed page and causes eyestrain in reading. In small amounts, coming from the pavement to the eye it discloses the inequalities of the road to the motorist at night or reveals the pedestrian in silhouette; in large amounts, as from snow in sunlight, it produces painful and serious injury to the eyes.

Fortunately, once the danger in direct glare and the advan-

Had only one row of units been employed in lighting this store, as is quite commonly the case with small stores, the center aisle would have been brightly lighted, but much less light would fall on the counters where most needed and a customer would inevitably cast a shadow on the merchandise. Note the soft even illumination shown in this illustration where correct principles have been followed

tages and disadvantages in specular reflection are understood, the means for eliminating the bad and retaining the good is readily available. The answer lies in proper diffusion of the light. The reflecting equipments now regularly manufactured provide any degree of diffusion considered desirable. The totally indirect type which directs all of the light to the ceiling, whence it is diffused throughout the room, represents the utmost in diffusion; the semi-indirect type, which directs a large proportion of the light to the ceiling, but transmits some through the bowl, provides a degree of diffusion which is preferred by many; so-called light-directing semi-enclosing, or totally enclosing, units are available in designs which provide good control of the light and satisfactory diffusion; enclosing globes of the proper size and density provide diffusion of the light but afford little control of its distribution. Open reflectors of proper design eliminate glare from the lamp filament but afford no protection against reflected glare in polished surfaces. Such reflectors, however, when designed for, and used with, bowl-enameled lamps constitute an equipment which is almost ideal for the large majority of industrial applications. They are inexpensive, easy to maintain, allow considerable control of the light distribution, provide good diffusion, and eliminate objectionable specular reflection while at the same time producing sufficient glint for the reading of a scale or the examination of textiles.

Color Quality of Illumination

Since an object is seen by the light which comes to it from the source and thence by reflection to the eye, it follows that color in the object is seen only when the light contains rays of that color. For example, a red object will appear black under light in which red rays are lacking or a blue object will appear black when blue rays are absent in the source. Daylight is composed of all the colors in proportions seen in the rainbow The light from Mazda lamps contains all the colors composing daylight but if the spectra, or rainbows, of the two were to be compared it would be seen that the Mazda lamp was richer than daylight in the orange-red region and weaker in the blue. For ordinary purposes, the light from clear Mazda lamps is sufficiently like daylight to answer all requirements, but where color discrimination is a factor, as in sorting or grading processes for example, and in the laundry where scorch marks must be readily distinguishable, or where the artificial light is used to supplement daylight, as in an office, daylight lamps, which screen out the majority of the excess orange-red rays, find wide application.

For purposes of color matching, dyeing, process printing, and the like, where extreme accuracy is necessary in the observation of colors, a still further correction of the light is necessary. For this service so-called color-matching units, which provide a light of true and unvarying north-sky quality, are available.

The high efficiency of present incandescent lamps which makes practicable the approximation, or the duplication, of daylight on a large scale also permits the modification of light to any desired extent for obtaining striking and unusual effects in display windows, in decorative lighting, and in the home.

Equipments designed especially for the control of color are readily available.

Shadow

Contrary, perhaps, to popular opinion, a certain amount of

Correct lighting for every service conforms to certain fundamental principles. Note the evenness of illumination, the absence of sharp shadows, and the bright and cheerful appearance of the interior

shadow is desirable in artificial lighting. Objects illuminated by perfectly diffused light appear flat and uninteresting, contours are lost, and it is difficult for the eye to form a correct judgment of the shape of an object. On the other hand, deep, black shadows are troublesome and are a source of constant danger because of what they may conceal. Shadows having a sharp edge or a series of sharp edges, which result from several small light sources near one another, are particularly annoying in office work, where they dance about the pencil point most disconcert! ngl3\ In general, in interior lighting, only soft illuminated shadows with gradually fading • outlines should b^ tolerated.

The number of shadows cast by an object and their length depends upon the number and the position of sources directing light toward the object ; the softness of the shadow depends upon the area of the surfaces from which the light comes and upon the number of directions from which light is received. Indirect and dense semi-indirect units which make the ceiling serve as the principal light source, and large units of the direct-lighting type, therefore, make for soft shadows, small units of the direct type make for sharp shadows. As a general rule, lighting units which are satisfactory for the application from the standpoints of light diffusion and low brightness will also prove satisfactory from the standpoint of shadow when a sufficient number are used to provide a satisfactory degree of uniformity in the lighting of the work.

Uniformity of Illumination

Where the prime purpose of lighting is the production of artistic effects, uniformity of illumination may be undesirable. On the other hand, it is not an uncommon experience to find in industrial plants that, because of too great a spacing between units, some workmen are supplied with only one half or one third as much light for their work as are others. Many office employees are forced to work under the same handicap. There are cases on record where the suspected incompetency of an employee with respect to his co-workers has been traced to the unsuspected cause of poor lighting.

Definite relations exist between the height at which units are mounted above the work and the distance by which they may be separated to provide reasonable uniformity in lighting, and light from a sufficient number of directions so that shadows will not prove troublesome. These relations have been reduced to simple tabular form for the convenience of the designer of lighting systems. In general, the permissible distance between units should not be more than one and one-half times the height of the light sources above the work; closer spacings can do no harm and are often desirable but when this spacing distance is exceeded, the illumination between units falls off very rapidly. The user of light should consider carefully before allowing his desire to keep initial costs low, lead him to install a system in which the proper spacing distance is materially exceeded.

Illumination of Vertical Surfaces

For many locations, such as offices and drafting rooms, light is required principally on horizontal planes, such as desk tops or table tops, and it has been the custom to calculate illumination on the basis of that delivered to horizontal surfaces with the assumption that the oblique surfaces of objects would be sufficiently lighted. This practice may result in inadequate illumination. In a machine shop, for example, the lighting of the vertical surfaces of the work or of machine parts is fully as important as

There is no necessity for imiKwing a handicap on any worker because of

poor hght. Though illumination requirements for drafting rooms

are comparatively severe on account of close visual application,

these requirements are met by the uniform, thoroughly diffused,

shadowless illuminafion of high intensity shown here

the lighting of the horizontal surfaces. As a matter of fact, most shops are lighted during the day by light from windows, which give a greater light on the vertical surfaces than on the horizontal. In all such cases where direct lighting is used, only those lighting units should be installed which show a reasonably good candlepower in the 50-70 degree zone as well as below these angles. A shop lighted by closely spaced automobile headlights directing the light downward from the ceiling would furnish ample light on a horizontal plane but such lighting would be far from satisfactory.

Desirable Wall Brightness

The effectiveness of a lighting system depends not only on the effectiveness of the lighting unit, but also on the reflecting properties of the walls, ceiling, and surroundings, and upon the size and proportions of the room. It is, in fact, entirely possible to find an installation of reflectors of poor design and inferior from the standpoint of glare, which is nevertheless, from the single standpoint of the percentage of light reaching the illumination plane, better than an installation where reflectors of good design are used, if the former are installed under favorable conditions such as light walls, ceiling, etc., and the latter under unfavorable conditions. On the other hand, it must be borne in mind that a large expanse of wall surface finished so light as to reflect a large volume of light into the eyes is objectionable for offices, residences, and all rooms where the occupants are likely to sit more or less directly facing the walls for considerable periods of time. Such data as are available indicate that where the brightness of the walls is equal to, or greater than, the brightness of white paper lying on a table or desk, annoying glare will result. In fact, a wall brightness one-half that of the paper has been found unsatisfactory — a brightness of one-fifth is, apparently, comfortable. With the usual types of lighting units, walls are not illuminated to intensities as high as those obtaining on desk or table tops, and walls which reflect less than 50 per cent, of the light which strikes them should not produce discomfort, providing, of course, that they are of a mat or semimat finish. Walls finished in buff, light green, or gray reflect about the proper proportion of light and their use is meeting with general favor. Walls finished in a high gloss are not satisfactory from a glare standpoint.

Maintenance

The experiences of those who have installed high levels of illumination prove conclusively that every foot-candle delivered at the work has a definite tangible value.

The man who provides a system capable of delivering 10 foot-candles at the work and then allows the system to depreciate until it delivers only 3 or 4 is losing not only 60 or 70 per cent, of the light he is paying for but, what is far more important, he is losing the profit on the difference between the output of his employees at this low level of illumination and their output at the higher level. If the depreciation of a lighting system were of the order of 2 or 3 per cent, or even 10 per cent. the matter would not be so serious a one, but surveys of installations in service show depreciations of 50 per cent., 60 per cent., and more. Many users are not getting one third of the light their systems are capable of delivering.

The lighting of the home should be flexible to permit lighting effects suitable to various occasions to be obtained, but in all cases, the fundamentals of lighting hold. Al! bright lights should be adequately shielded from view, though enough light should be available for reading or sewing comfortably.

Part II Illumination Design Data

To take the several essential factors entering into illumination design properly into account has appeared so complicated a task that many designers have adhered to rule-of-thumb methods w^hich, while adequate in some cases, are likely to lead to unsatisfactory. results when applied generally.

The method of design here presented will be found fully as simple as any of the common short-cuts. It has the decided advantage that the technical considerations wjhich are important as influencing the result and which require the experienced judgment of the engineer have been taken into account in the preparation of the charts and tables and therefore automatically receive due allowance in the lighting design. Hhe data apply in interiors where standard types of reflecting equipment are used to obtain general lighting of substantially uniform intensity.

The four steps to be carried out in the design of a general lighting system for a room are :

1. Decide the foot-candle illumination required.

2. Select the type of lighting unit best adapted to the location.

3. Determine the location of outlets, the mounting height and number of lighting units required.

4. Ascertain the size of Mazda lamp which will provide the foot-candles desired.

I. Foot-Candle Illumination

Tables 3 and 4, pages 25 to 31, list the foot-candle values, corresponding to present standards, for different classes of industrial operations, offices, stores, etc. The desirable illumination

DEFINITIONS

Lumen: The lumen is the unit of light flux quantity. The number of lumens required to light a Riven surface is proportional to the illumination in foot-cajidles and to the area of the surface in square feet. The light output of Mazda lamps is given in lumens.

Foot-Candle: The degree to which a surface is illuminated is measured in foot-candles. One lumen will light a surface of 1 square foot to an average intensity of 1 foot-candle.

Coefficient of XTtilization (Percentage of Lumens Eff^ective) : The proportion of the lumens generated by the lamps which reaches the plane of work is known as the Coefficient of Utilization. It is dependent upon the type of diffusing and reflecting equipment, color of walls and ceiling and also the proportions of the room, that is, the size and shape of the room and the height of the light source above the plane of work. These room proportions are classified in this section by Room Index tables. The plane of work, unless otherwise specified is ordinarily considered to be horizontal and 2J4 feet above the floor.

Depreciation Factor: This represents a safety factor which provides added initial illumination sufficient to compensate for acing of the lamps and the falling off in reflecting efficiency of the reflectors, walls, and ceilings due to deterioration and the collection of dust and dirt. A depreciation factor should always be applied to the recommendations for foot-candles of illumination since these are always stated in terms of average service, or sustained illumination.

varies rather widely depending on the conditions in any particular installation, such as the accuracy of the operation and fineness of detail to be observed, the color of goods worked on or handled and, in the case of stores, the advertising value resulting from the attractiveness of a well lighted interior. The foot-candle values recommended in the table are the minimum to be adhered to if fully satisfactory lighting is to be assured. Under particular conditions considerably higher illumination is often desirable.

2. Type of Lighting Unit

The selection of the type of lighting unit depends not only upon the requirements of the work but in some cases upon the construction of the room and the color of ceiling and walls. For example, semi and totally indirect lighting is unsuited to rooms with very dark ceilings. It is important to specify the type of lamp to be used since, for example, as shown in Table i, bowl-enameled lamps used in open reflectors, such as RLM standard domes, form a much superior lighting unit from the standpoint of glare, reflected glare, and shadows than clear lamp units of the same type. In general, clear Mazda C lamps should not be used in open reflectors where the mounting height is less than 20 feet.

Factors other than those listed in Table I may enter into the choice of the lighting unit in certain instances. For example, in stores, offices and other public installations, decorative eflfect is often an important item. The charts on pages 21 and 22 rate the various types of units comparatively to serve as a basis for judgment of the adaptability of a unit for a particular class of installation.

3. Location of Outlets, Mounting Heigjit, and Number of Lighting Units

Make a diagram to scale of the floor area of the room. If the units are of semi or totally indirect type, measure the ceiling height of room and refer to Table 2-b, page 24, for the permissible spacing of units and preferred suspension distance of lighting units corresponding to this ceiling height.

If the units are of direct lighting type, determine the mounting height and refer to Table 2-a for the permissible spacing corresponding to this mounting height. If the units are mounted as close to the ceiling as possible (a minimum allowance of (me foot is usually necessary to provide for the drop of the reflector from the ceiling), a wider spacing is permissible and fewer units are therefore necessary for an even distribution of light. Considerations of shadows, appearance and arrangement of work may make a lesser mounting height desirable even though a closer spacing of outlets would be needed to keep the same uniformity of illumination. Ordinarily lamps should not be mounted less than lo feet above the floor unless a low ceiling makes it necessary.

Having determined the permissible spacing proceed to locate the outlets on the diagram of the floor area. Locate the units as nearly symmetrically as possible without appreciably exceeding the permissible spacing for uniform illumination. At a greater height, a spacing closer than that in Table 2 results in greater freedom from shadows but increases the number of units required and makes the installation cost more. If a spacing somewhat clo5ier than the permissible value is adopted, as is often the case, it is allowable, though not necessary, to refer back to Table 2 and select a lower mounting height corresponding to the new spacing. The distance between the outside row of outlets and the wall should not exceed one-half the spacing distance. For office spaces, or where work is carried on at benches or machines near the wall, this distance should be approximately one-third the spacing distance. 4. Lamp Size

After the outlets have been located on the plan, the lamp size to be used may be determined by the following calculation :

A

Area in Square Feet Total Floor Area in Square Fee t Per Outlet — Number of Outlets

B ^Re^ uired^ er - ^Qot-Candles x Depreciation Factor

Square Foot ~ Coefficient of Utilization

Lamp Lumens Area in Square Feet Lamp Lumens Required C Required per = | per Oudet X per Square Foot

Outlet (From A) (FromB)

Foot-Candles — Illumination decided upon.

Depreciation Factor — Safety factor or allowance for depreciation due to aging of lamps, dirt, dust, and deterioration of reflecting value of walls. Use 1.3 for fairly clean locations. Use 1.5 for dirty locations or where cleaning is infrequent.

Coefficient of Utilization — Proportion of the generated light from the lamps which reaches the plane of work. The Coefficient of Utilization Sot thp inst^jbtion is determined as follows:

Table 5, pages 32 to 35, shows that the CocHicient of Utilization varies according to the type of fixture, the proportions of the room expressed by **Room Index," and the color of the walls and ceiling. From the "Room Index" Table 6, pages 36 to 42, find the Room Index corresponding most nearly to the dimensions of the installation. Then the Coefficient of Utilization for the installation of the type of lighting unit selected will be found from Table 4, in the proper column ol wall and ceiling color opposite the correct Room Index.

Having determined the lamp lumens required per outlet by ihe above calculations, the wattage of Mazda lamps to be used may be found by reference to Table 7, page 43, which lists the lumen output rating for each size of Mazda and Mazda Daylight lamps. Locate in this table the size of lamp of the desired type which most nearly meets the requirement of lumen output. When the lamp lumens required fall nearly midway between two sizes, choose the larger rather than the smaller, unless it is certain that the less illumination from the smaller will suffice.

Computed Illumination Values

The foot-candles of illumination in service, allowing a depreciation factor of 1.3, obtained for systems having different Coefficients of Utilization and areas per lamp are worked out in Table 8, pages 44 and 45. Table 8 can be referred to as an approximate check on design computations made as outlined above.

ILLUMINATION DESIGN FOR A FACTORY ROOM

The floor plan of the factory space to be lighted is 60' x 120' as shown.

The work carried on in the room is assembly of sewing machine heads.

Height of floor to roof trusses is t2 feet.

The roof is of sawtooth construction and the walls and upper structure are painted a medium color. A considerable amount of dark material is kept stacked along the walls of the room.

Following the steps outlined on Pages 14 to 17 the lighting design is determined as follows:

1. Foot-Candle Illumination

From Table 4, Page 27, 8 foot-candles are recommended for assembly, medium grade.

2. Type of Lighting Unit

Consulting the Guide to the Selection of Reflecting Equipment of Table i, Page 21, Unit No. 2, the RLM dome with bowl-enameled lamp is selected based on efficiency and favorable showing from the standpoints of glare, reflected glare, shadows, and maintenance.

3. Location of Outlets, Mounting Height, and Number of Units

The height of the benches and therefore the plane of work is sl^\ above the floor. The maximum mounting height of the lamps above the floor is 11' (12' height from floor to truss less i' allowed for reflector drop). Hence, maximum mounting height of units above plane of work is 11' — 3^' or 7y2.

From Tauitf 2-a of Spacing-Mounting Height, Page 23, a ^Vi mounting height above plane for direct lighting units is found to indicate a permissible spacing of approximately 11' and since the section of the room near the walls consists of aisles and storage, 55^' may be allowed for the distance between the last row of outlets and the side walls. Reference to floor plan of the room shows that a 16' spacing each way (outside units 5' from walls) would make a symmetrical layout in the 2o'x3o' bays and this spacing is therefore adopted. Outlet locations for the entire space are marked on the plan as shown and 72 are found to be required.

4. Lamp Size

i^A) Area in

Square Feet per Outlet

Total Floor Area in Sq. Ft. 7200

Number of Outlets in Room h

! i tt n \ f- n \ n a \ u ain n I « fi \ a a n ti f

« tj a )3 n

I

I

« I n I I

I

H n a n o tfOt^Td brVBOwan bowl enameled MAZDA C toLmp.c<jwipped *i»h anQLM St«nd&Td D6rotQefledor.wi»h swilabte holder. Cefieclor localed U feel above Ihc floor

R^qlur^dTer^= ^QQt-^^"<^^^s x Depreciation Factor _ 8 x 1.30 _ Square Foot Coefficient of Utilization .57

= 18.2

Coefficient of Utilization

Area in square feet per outlet— 100.

Depreciation Factor — 1.30.

To find Coefficient of Utilization.

From Room Index, Table 6, page 37, in a room 60' x 120', where the mounting height of direct lighting units above plane of work is 7', the Room Index is 5.0 or from Page 38 in the same room where the mounting height is S' the Room Index is 4.0. Either value might be used for the Room Index with equal accuracy as to the result but 4.0 is more conservative.

Referring to Table 5, Coefficients of Utilization, Page 32, for RLM dome bowl-enameled lamps in a location with a Room Index of 4.0 and where the ceiling and walls are fairly dark the Coefficient of Utilization is found to be .57. (C) Combining (A) and (B)

Lamp Lumens Area in

Required per = Square Feet Outlet per Outlet

Lamp Lumens X Required per = 100 x 18.2 = 1820 Square Foot