READERS OF THIS department and friends of Russell Porter-those who have seen him and those who hope to-have asked many times since World War II began what he was doing. Though your scribe has exchanged letters and notes, containing innumerable enclosures of a telescoptical nature, with Porter for 20 years, entertained him at home and been entertained at his home many times, attempts to find out what he was doing in connection with the war just didn't get anywhere. He was under the same seal of secrecy as all who were doing hush-hush work.

With the war over, a campaign of teasing and wearing down was begun on Porter and has at last produced the following response, in reply to the argument that, sometimes, too much modesty is almost immodest. Porter's note:

Perhaps, at that, the A.T.M.s might be interested to know what I have been doing since Pearl Harbor when the 200" telescope had to be entirely laid aside. I had expected a comparative holiday for myself while the world was fighting but was amazed to find myself working harder than ever.

As you know, the California Institute of Technology was allocated several war projects to develop, through the Office of Scientific Research and Development, and the officials here soon found that my ability to visualize and put on paper military weapons, before they were actually built and tried out, would many times be useful to them when submitted to the Brass in Washington. I made so many of these drawings-several hundreds of them-that I was finally nicknamed in the capital "The Cutaway Drawing Man."

At first, we here on the Pacific Coast were preparing for invasion by the enemy, and many were the projects put forward to meet it. Later, as our forces moved into enemy territory, a vast number of offensive weapons were devised and many of them put into production. A major effort was the application of rockets to all kinds of purposes-planes, landing craft and jungle warfare. "Cal Tech" has already been cited by the Government for its contribution to this effort, and more than one discharged marine has entered my office and spoken almost lovingly of those "jet busters" and how they confused and annihilated the Japs.

It is common knowledge that southern California has been and is a hotbed of proving grounds, scattered in remote areas in the desert, where all these gadgets are tested. A good example is at Inyokern, some 200 miles from here. It is a Naval Ordnance test station and is larger in area than the State of Rhode Island. I spent many days there-just drawing. Here are a few examples of the jobs they threw at me.

Go out and draw a perspective of---Station, taken from 20,000 feet up and looking northeast.

Draw an invasion by landing craft at Guadalcanal, showing an air view of the craft formation, the enemy emplacements and surrounding scenery. (Here, for the palm trees and the streams, I levied a good deal on photographs in Life, but not wholly.)

Make a cutaway drawing of the fuse in the head of rocket. This device is as complicated and delicate as a watch and I was hard put to it but finally succeeded. Oh yes, and the drawing must be in tomorrow. "Oh hell," says I, "I'm an old man and the doc insists I take my siesta." "Too bad," they reply, and add, "Take it easy, Porter." Then, as an afterthought, "but the drawing must be in tomorrow." [A masterpiece of understatement through omission. That particular job put Porter in bed for a week.-Ed.]

Then there was that fantastic thing, the Jap paper balloon. They had to have one of Porter's drawings showing it dissected. Down in one corner I drew a tablet with four Japanese inscriptions on it. Translated, it meant roughly, "inefficient." They launched some 10,000 of 'em. A few reached our coast but little damage was done.

Then there were those wind tunnels and water tunnels-the latter being glass tanks filled with water into which they shot models of rockets.

Well, it was all pretty much fun in a way. That is to say, interesting. And there were breaks. One night Humason phoned from Mt. Wilson. "Get into your car and up here as soon as you can. Mars is high up in the heavens, and the seeing is fine. "When I got there the seeing had gone bad but it slowly improved toward dawn. I worked at the Cassegrainian focus of the 100" but found no canals to draw. I thought this might displease the astronomers, but, no, quite the opposite."

End of Porter's note and now you know that when they wrapped up the 200" telescope in mothballs for the duration while they turned to the production of war optics they didn't wrap Porter up with it. And since you now are sure to ask about the present status of that job, we have asked Porter to add a word. "The mounting," he writes, "is nearly ready to receive the mirror. The mirror is in the last stages of figuring, and lacks only a few wavelengths of a paraboloid. Mopping up the small odds and ends will take less than a 1 year."

With his war contribution completed, Porter, at 74, is taking some well-earned rest, as shown in Figure 1, which does not, however, show a cutaway of his house. If it did you would see down cellar a neat machine he has designed and built, plugging away on some 8" flats while he reads. Porter has sent us a drawing of that machine and promises detailed data on it for a later number.

Throughout his 18 years at Pasadena, Porter has often itched to escape clean handed duties and get into the shop ant push glassthe same as any other amateur, and has never been so happy as when circumstances permitted his doing it (Figure 2). With all his contacts with the topflight people in science and optics he has never lost that urge. He expects to come to Stellafane for the big get-together of amateurs August 3 and 4, there he will give a talk about everything you'll think of wishing to hear about-his two years' work on the famous rockets "Tiny Tim" and "Holy Moses," also the revelations of the electron microscope at 60,000 diameters on unused and used particles of polishing abrasive.

FROM time to time new experimental research tends more and more fully to vindicate the molecular flow theory of the nature of the optical polishing phenomenon, as against the old-fashioned, microscopic scratch theory-that is, that polishing was the same as grinding, except on a finer scale. A paper delivered by Dr. Lloyd Motz of Columbia University and The Optical and Film Supply Company, New York, published in the Journal of the Optical Society of America, Volume 32, pages 147-148, further bears out the validity of the molecular flow theory. This theory is sometimes called the "butter" theory and at one time was looked at as perhaps a bit wild. The following is quoted from the paper mentioned above:

"Rayleigh was one of the first to show by means of the microscope that polishing a surface is a process different from that of even the finest grinding; he concluded from his microscopic studies that polishing is a molecular phenomenon caused by the adhesive forces between the molecules of the polishing agent and those of the surface. Beilby added further to this idea by demonstrating that the polished layer resembles a film of viscous liquid and appears amorphous (in the case of polished crystalline solids) to the highest powers of the microscope. An examination of a polished surface with a microscope shows that the pits and scratches of the previous grinding are not eliminated by a wearing down of the surrounding surface but rather that these scratches are filled in by a flow of the surrounding material.

"Where one is dealing with a crystalline solid, the study of the polishing process is made easy by the fact that the polishing destroys the crystalline nature of the surface and builds up an amorphous layer. One can investigate the thickness of this layer for crystalline substances by dissolving the layer in a suitable acid until the underlying crystalline structure is reached. Thus in the case of calcite N. K. Adams reports that the completely amorphous layer was roughly 50 angstroms thick and that the flow lines produced by the fibers of the moving wash-leather were found at depths of 250-500 angstroms and some traces of the original ground surface down to 5000-10,000 angstroms.

"In the case of amorphous substances such as glass the investigation of the depth of the polished surface is difficult since there is no underlying crystalline structure upon which the polished surface rests. That the polished surface is, however, different in structure from the underlying glass can be easily demonstrated by subjecting the polished surface to the action of dilute hydrofluoric acid.

"If the polished surface is placed in dilute hydrofluoric acid for a short time, the high polish is not in general destroyed, but the surface becomes covered with innumerable scratches and pits of varying length and depth. Although many of these scratches exhibit a curvature which might be ascribed to the circular motion of the fine grinding machine, the evidence that these scratches are those originally produced in the glass by the fine or rough grinding before the polishing began is not conclusive. Another explanation which might be offered to account for these scratches is that, as the polished surface is etched off by the acid, the rearrangement of the molecules in the newly formed surface gives rise to stresses which cause the surface to crack.

"Although we may not conclude that all the scratches which appear after the acid treatment were present before the surface was polished, the following simple experiment demonstrates that scratches which are present on the surface before the surface is polished will reappear after polishing if the surface is treated with hydrofluoric acid.

"On a highly polished glass surface (hard crown-glass) several faint scratches of definite shape (letters and geometrical patterns) were traced by means of a steel razor edge. The surface was then placed on the polishing machine and rouge-polished until no trace of the original scratches could be discerned even under a microscope. The surface was then placed for a few minutes in a very dilute solution of hydrofluoric acid and then carefully examined. All the marks scratched on the surface by the razor edge reappeared in a more pronounced form than they originally had.

"It is clear from this result that the process of polishing is a molecular one: the forces of adhesion between the molecules of the polishing agent and those of the glass cause the glass surface to flow and fill up the cracks, pits and scratches. This filling up process, however, does not obliterate the scratches-in the sense that no distinction exists between the polished layer and the underlying surface. The action of the acid seems to indicate that the glass which has flowed into any surface deformities as a result of the polishing is more loosely bound to the surface than the surrounding glass and is therefore more easily removed by the acid.

"These results are of some importance in considering the degeneration which polished surfaces may suffer if not sufficiently protected over long periods of time. However highly polished and free of defects a surface may appear, it will, if not well protected from acid influence, develop scratches after a sufficiently long period of time."

HOGGING out a deep curve ("soup bowl") for a Schmidt primary is an endless job if done in the orthodox way. In The Observer, periodical published by the Franklin Institute, Philadelphia, Web Phillips describes a short cut:

"The tool is placed on the spindle and rotated at medium speed while the mirror is held in the hands against the edge of the tool at an angle of about 30 degrees to the horizontal. Wet abrasive deposited on the mirror with a brush and the mirror is rotated slowly in the hands as it is held against the tool The action is slow at first until the sharp edge of the tool is ground off then it becomes increasingly rapid.

"Eventually the curve on both the mirror and the tool will cover sufficient area to permit curvature control by length of stroke and from this point o the mirror is ground by convention methods."

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