tion intensity on a picture area of 150 square feet is seen to be in excess of 5 foot-candles.

The question of the most desirable intensity for motion picture projection is one on which a difference of opinion still exists. The Committee on Glare of the Illuminating Engineering Society14 has recommended a brightness for the picture corresponding to a screen illumination of 2.5 foot-candles with no film in the machine, with a factor of 5 either way. A brightness which is too high causes not only fatigue to the eye, but also makes the flicker, wandering of the arc, etc., more pronounced. It appears that the present highcurrent arc installations are operating in the upper range of desirable intensities.

BIBLIOGRAPHY

GENERAL PRINCIPLES OF LIGHT PROJECTION

BENFORD, F. A., JR.-"The Parabolic Mirror;" Trans. I. E. S., Vol. 10, p. 905. GAGE, S. H. and H. P.—“Optic Projection," Comstock.

NATIONAL LAMP WORKS OF G. E. Co.-" Mazda Lamps for Projection Purposes;" Eng. Dept. Bulletin No. 23.

ORANGE, J. A.-"Photometric Methods in Connection with Magic Lantern and Moving Picture Outfits, and a Simple Method of Studying the Intrinsic Brilliancy of Projection Sources;” G. E. Review, Vol. 19, p. 404.

PORTER, L. C.-"Photometric Measurements of Projectors;" Lighting Journal, Vol. 4, p. 7.

"New Developments in the Projection of Light;" Trans. I. E. S., Vol. 10, p. 38.

AUTOMOBILE HEADLIGHTING

CLARK, EMERSON L.-"Automobile Lighting from the Lighting Viewpoint;" Bull. Soc. Auto. Engs., April, 1916, p. 45.

Discussion. "Headlight Glare;" Bull. Soc. Auto. Engs., Feb., 1916, p. 296.

Symposium.-"Glare-Preventing Devices for Headlights;" Trans. Soc. Auto. Engs., Vol. 9, Part II, p. 284.

RAILWAY HEADLIGHTING

American Ry. Master Mechanics Ass'n.-"Report of Headlight Committee,"

1914.

Ass'n. of Ry. Elec. Engineers.-"Report of Committee on Locomotive Headlights;" Ry. Elec. Eng., Vol. 5, p. 199.

BABCOCK, A. H.-"Southern Pacific Six-Volt Electric Headlight Equipment;" Ry. Elec. Eng., Vol. 7, p. 233.

14 Committee on Glare, "Diffusing Media; Projection and Focusing Screens, "Trans. I. E. S., Vol. II, page 92.

BAILEY, P. S.-"Incandescent Headlights for Street Railway and Locomotive Service;" G. E. Review, Vol. 19, p. 638.

HARDING, C. F., AND TOPPING, A. N.-"Headlight Tests;" Trans. A. I. E. E.

Vol. 29, p. 1053.

MINICK, J. L.-"The Locomotive Headlight;" Trans. I. E. S., Vol. 9, p. 909. PORTER, L. C.-"Meeting the Federal Headlight Requirements;" Ry. Elec. Eng., Vol. 7, p. 468.

Ry. Elec. Engineer, Vol. 3.-"Electric Headlights-Wisconsin Railroad Commission Tests."

SCRUGHAN, J. G.-"Electric Headlight Tests;" Ry. Elec. Eng., Vol. 5, P. 349.

Symposium (SUGG, CHAS. R., Dennington, A. R., PORTER, L. C.).—“ Theory, Design and Operation of Head-Lamps;" Elec. World, Vol. 62, p. 741.

SEARCHLIGHTING

BLONDEL, A.-"A Method for Determining the Range of Searchlights;" Illuminating Eng. (London), Vol. 8, pp. 85, 153.

CHILLAS, R. B., JR.-"Searchlight Carbons;" Journal of U. S. Artillery, March-April, 1916, p. 191.

Electrical World.-Vol. 64, p. 181; "Search Lamp with Vapor-cooled Electrodes" (Beck). Vol. 68, p. 611; "High-Intensity Searchlight for Governmental Purposes" (Sperry).

MCDOWELL, LIEUT, C. S.-" Searchlights;" Proc. A. I. E. E., Vol. 34, p. 195. "Illumination in the Navy;" Trans. I. E. S., Vol. 11, p. 573.

NERZ, F.-"Searchlights; Their Theory, Construction and Applications;" Van Nostrand.

Symposium (LEDGER, P. G., AYRTON, MRS. HERtha, Trotter, A. P., etc.) -"Searchlights; Their Scientific Development and Practical Applications;" Illuminating Eng. (London), Vol. 8, pp. 53-84.

WEDDING, W.-"A New Searchlight" (Beck); Electrotechnische Zeitschrift, 1914, p. 901.

FLOOD LIGHTING

BAYLEY, G. L.—“Illumination of Panama-Pacific Exposition;" Elec. World, Vol. 65, p. 391.

Elec. Review and Western Electrician, Vol. 67, p. 1104; "Indianapolis Bank Adopts Flood Lighting." Vol. 67, p. 724, "Flood Lighting of Building Fronts from Ornamental Cluster Posts."

Electrical World, Vol. 67, p. 1173; "Flood Lighting a Flag;" Vol. 67, p. 1462; "Adding Hours to Summer Days for Outdoor Recreations." Vol. 68, p. 453; "Niagara Falls Flood-Lighted."

HARRISON, WARD and EDWARDS, EVAN J.-"Recent Improvements in Incandescent Lamp Manufacture;" Trans. I. E. S., Vol. 8, p. 533.

Lighting Journal, Volume 4, p. 18; “Projectors for Flood Lighting."

MACGREGOR, R. A.-"Lighting the Soldiers' and Sailors' Monument;" Ltg. Journal, Vol. 4, p. 175.

MAGDSICK, H. H.-"Flood Lighting the World's Tallest Building;" Elec. World, Vol. 68, p. 412.

PORTER, L. C.—"Pageant Lighting;" Ltg. Journal, Vol. 3, p. 169.

RYAN, W. D'A.-"Spectacular Illumination;" G. E. Review, Vol. 17, p. 329. "Illumination of the Panama-Pacific International Exposition;" G. E. Review, Vol. 18, p. 579.

SUMMERS, J. A.-"Flood Lighting the State House at Boston;" Ltg. Journal, Vol. 4, p. 2.

UHL, A. W.-"Flood Lighting of a Great Outdoor Pageant;" Ltg. Journal, Vol. 4, p. 172.

LIGHTHOUSES

Encyclopædia Brittanica, 11th Edition.

HASKELL, RAYMOND.-"Lighthouse Illumination;" Trans. I. E. S., Vol. IO, p. 209.

MACBETH, GEO. A.-"Lighthouse Lenses;" Proc. Engs. Soc. Western Penn., Vol. 30, p. 231.

LIGHT SIGNALS

CHURCHILL, Wм.—“Red as a Danger Indication;" Trans. I. E. S., Vol. 9,

p. 371.

GAGE, H. P.-"Types of Signal Lenses;" Trans. I. E. S., Vol. 9, p. 486.
LUCKIESH, M.-" Color and Its Applications," Van Nostrand.

MCDOWELL, LIEUT. C. S.-"Illumination in the Navy;" Trans. I. E. S., Vol. 11, p. 573.

SAUNDERS, J. E.-"Recent Developments in Light Signals for Control of High-Speed Traffic;" Elec. Journal, Vol. 13, p. 443.

STEVENS, THOS. S.-"Illumination of Signals;" Trans. I. E. S., Vol. 9, p. 387.

PROJECTION OF TRANSPARENCIES

CHILLAS, R. B., JR.—“Projection Engineering;" Trans. I. E. S., Vol. 11, p. 1097.

GAGE, S. H. and H. P.-"Optic Projection."

ORANGE, J. A.-"Optic Projection as a Problem in Illumination;" Trans. I. E. S., Vol. 11, p. 768.

TAYLOR, J. B.-"The Projection Lantern;" Trans. I. E. S., Vol. 11, p. 414.

THE ARCHITECTURAL AND DECORATIVE ASPECTS OF

LIGHTING

BY GUY LOWELL

There is surely no scientific profession, there is no branch of the engineering fraternity for which a thorough artistic training is more desirable than the profession of illuminating engineering. We can see, however, by looking over the list of lectures in the usual engineering courses that the technical knowledge which one should have is so great-there are so many scientific subjects to be discussedthat there can be but little time left in the curriculum for the study of the fine arts. Yet after all the aims of the illuminating engineer and of the artist are similar-it is to reach the mind through the eyes. The point of view of the engineer is, however, largely objective. He often seems to think that his mission is ended when he has made it possible to convey to the mind the facts-as they are. The artist idealizes and wishes to state the facts as they might or should be, or as we say, colloquially, he wants to show them in the best possible light. These two methods of seeing the subjective method and the objective method, are often not very different, and I want to spend my time this morning considering the common aims of the illuminating engineer and the artist, and show how close together the paths of the two really lie.

We have been taught that were it not for the reflected light that comes from all the different objects on this earth of ours, our world would appear to be in darkness, because we could not see the objects. around us. There might be sources of light, like the fire, the incandescent filament, or the electric arc which would be visible in themselves, but the light that comes from the heavens or from some manmade source must be reflected from an object in greater or less intensity for us to be able to see it. Furthermore, we all know that the effect that an object makes on the retina and thereby on the mind is dependent on the way the light is reflected from an object, and partly therefore on the way the light falls on that object.

Since it is this pattern made by rays of varying intensity and of varying color on the retina, calling up various reminiscences to our mind, that enables us to see-to understand what lies before us, it

follows that the type of lighting that sets in motion the most powerful train of associative ideas is the one that may have the greatest emotional effect; but the intensity of the emotional effect is not measured by the intensity of the light even though the intensity of that light may affect the clearness with which we judge of the physical aspect of the object on which it falls. We are not always necessarily interested, however, in the physical aspect—in the intricate details of the object at which we are looking. We are often more interested in the memories it calls up. Let me illustrate what I mean by an example.

When I realized some weeks ago that I was going to talk to the members of this society on the æsthetic principles instead of the scientific principles involved in some of the every-day problems of lighting, it occurred to me to get a variety of opinions on the mental reaction produced by such a simple source of light as one bright star in the midnight sky. So I asked three people among my neighbors-one a distinguished astronomer, the next a young girl just back from college, and the third an immigrant woman whose husband worked as gardener on the place what their thoughts would be were they to wake up in the middle of a wintry night, and as they came back to consciousness were to see through the window a bright star. The astronomer said he would begin to wonder which star it was among all the myriads in the heavens; the young girl with a mind full of classical poetry said she would think of the mythological stories connected with the stars; the working woman said,

Sure if it was a single star on a wintry night I would think of the Star of Bethlehem."

But when I said to each one of my three friends, "Supposing you were told that it was not a star after all but a distant electric light, what would you do?" They all three made a similar answer, "We'd turn over and go to sleep."

Now the interest in these answers lies here. No one of the three was interested in the one little bright spot in the sky as a source of light; so long as it was a star, it called up a whole series of associative thoughts.

Whether it calls up with its suggestion of infinite distances and infinite time a whole theory of cosmic philosophy; or whether it suggests to the pagan mind the mythological intrigues of a Jupiter, a Mars and a Venus; or whether the star recalls one of the most touching stories of our Christian faith-the story of the Star of Bethlehem seen by the watching shepherds from the hillside nearly