And now Bugbear No. 2 is also on the way out. You whose dispositions have been wrecked by pitch lap making may make your salaam to four modest men in Pittsfield, Mass. and Bridgeport, Conn.- Everest, Munn, Morse, and Carlson, for these benefactors have now taken the bug out of the second bugbear. Thanks to them you can now make a lap in your sleep, that is as uniform and perfect as a waffle. The Pittsport Door Slat is the answer. The picture shows (bottom half) what the P. D. M. is like, and the series of pictures on the page you are reading shows just how it is used. It is a specially designed, specially made grid of flexible rubber which you lay on the glass tool, fill with melted pitch, strip off and, lo, your lap is made and without any of those idiosyncrasies which, as you well know, will somehow or other turn up in an ordinary pitch lap no matter how much profanity you direct at it while working on it.

Closely examine the photograph (left). The mat, when ready for use, looks as shown at the bottom. Its thickness is 3/16", its size 12" x 12", and the grid is made up of members of flexible rubber cast in one piece and having a cross-section like that of a typical channel in a pitch lap-that is, l/4" wide at the side which casts the top of the channel, and about half as much at the side which lies on the glass tool and makes the bottom of the channel. The mat gives facets one inch square and all alike. When the door mats first come from the manufacturer there is a thin rubber web over the whole of one side, and this must be cut away before the mat can be used. At the top of the same picture that job is shown partly done. A sharp chisel or sharp wet knife is the best tool to us for this Of course, the manufacturer could himself do this job but the mat would then cost you more than the dollar it does cost, hence you get the mat plus some exercise, and no extra charge for the latter.

To use the door mat, according to Everest, you place the tool, face up, on a table and tie a string loosely around it, or snap on a rubber band or two. Then you lay the mat on top-all as shown in Figure 1.

Next insert cardboard strips around the edge, for dams (Figure 2). Everest says that pitch applied in such small amounts as one facet at a time (as you will see later has no tendency to creep under the rubber or through little openings around these dams. He also writes: "We make our laps on a clean white table cloth, as shown in the photos." However, if your wife hasn't the fine disposition his has, we advise the addition of a bed pad.

Now (Figure 3) pour melted pitch into each of the square openings, using a spoon. This same photograph shows-at least the original does-the famous unruly Everest hair which Porter immortalized in a sketch in A.T.M. It seems that when Wallie was rounding a shoulder of Pike's Peak, on his way to California in '49, a big grizzly bear suddenly reared up near him and his hair instantly reared up too. Since then he never could make it lie down or do a thing with it.

Figure 4 shows the squares full of pitch. Of course it will occur to anyone to pour them all to about the same depth. Now chill the lap under a cold water tap and (Figures 5 and 6) peel off the door mat. It won't stick, and when it is first put on it needs no goose-grease to keep it from sticking.

Now soften the lap under the hot water tap and press it to contact with your mirror. Then trim off the little irregularities caused by pressing-a simple matter, as Wallie says, like the small trimming you have always done on laps in order to keep the channel open during a polishing job.

Figure 7 is the finished job-hold up the page and squint your eye along both sets of channels. Isn't it a dandy? Here is what Dr. S. H. Sheib of Richmond, Va., who borrowed your scribe's door mat, has to say:

"Dear Doc: I have tried out the door mat lent me and find that it does everything that is claimed for it. These gentlemen deserve the gratitude of all telescope nuts for relieving them of the abominable and profane job of channeling pitch. Removal of the web is easily effected, as you have suggested, with a sharp 1" chisel, but may be done equally well, though more slowly, with a sharp wet pocket knife.

"In making the lap one must remember, of course, to smear the top of the tool with turpentine, and to place the center of the tool at the corner of one of the facet squares in the regular manner. This done, it is difficult to imagine how even the most inexperienced worker can fail to make a perfect lap every time. There is no need for rush or hurry-if interrupted at any stage, the work may be set aside and resumed at any later time without risk of injury to the lap. The V-shaped ribs of the grid show no disposition to cling to the pitch, provided the whole is well cooled after the squares are filled, but part readily, leaving beautifully straight, clean, smooth channels without a trace of pitch on the bottoms."

In the final photograph of the series you see Wallie testing by finger nail for hardness on his pet scale, which you will find added to page 364 in the new edition of A. T. M.

We asked Everest whose baby this new thing is and he says that the "only" thing he can take credit for is the idea. He says Ralph Munn then made the mold and the preliminary samples, but had a little trouble getting perfect door mats, and so he accepted the offer of H. F. Morse to complete the development at Bridgeport, Conn., where they have had more experience with such things, and Morse was assisted by G. Carlson, also of Bridgeport. Morse then "made arrangements," Everest says, "with a manufacturer to supply door mats at a dollar each to any of the maniacs who desire them."

A lot of the above must sound much like a sales talk but, if so, it can't be helped. and no apology is offered to the cockeyed world for it. The four who got up the door mat aren't making anything from it, and their only idea was to find a rubber goods manufacturer who would undertake to bother with it. They found that door mats could be made and sold, non-profit, for about 75 cents plus postage. Blame your scribe for suggesting that the price therefore be set at an even dollar, postage free anywhere within the confines of the planet. It is true, this penalizes the nearby purchaser for the benefit of the distant one, but it saves a lot of preliminary bother about ascertaining mailing costs to all sorts of out of-the-way places and the "injustice' probably will not seriously affect anyone.

AS there still seems to be uncertainty about the degree of refinement required of a good optical surface, three recent illustrative focograms are reproduced on this page. The job shown above was ground and polished by an amateur, as the Pyrex, perforated primary mirror for a 12-1/2" Gregorian. The mirror is approximately an f/5. The owner says he sent his mirror to a man who offered to refigure mirrors and that, when he sent it, there were no scratches on it. A fee of 25 dollars had been quoted for its correction, he says, "up to any measurable error. " This focogram represents the mirror when he got it hack. Not only is the surface deeply scratched and scored in many p1aces, but it is very lumpy in the small areas not scratched. Study the reproduction closely. The Ronchi bands also were zigzag, the owner writes, "like a snake."

Of course 25 dollars was too little in the first place, to charge for refiguring a 12-1/2" mirror-far too little. Men like Pierce or Tinsley or Lower would probably ask much more, and rightly so. But a promise that can't reasonably be kept should perhaps not be too freely made, in the first place.

The figurer, when the matter was submitted to him by Scientific American, after the owner had failed to get result offered to refigure this mirror. But in the meantime the owner had decided to do it himself, and he was able to his own surprise, to produce the result shown at the top. We leave it to the reader to judge which is the better of the two.

The job at the bottom of this column is the 8" primary for an f/5 aplanat, an was entirely made by Mary A. (Mrs. A. W.) Everest, 15 Allengate Ave., Pittsfield, Mass., with the moral and intellectual support of her husband, Wallie Everest. She made free use of his advice, but slapped his hands whenever he tried to touch the mirror, and he is considerably prouder of it than she is. Three 1/4" scratches and one 3/4" scratch show on the original focogram, but they are so fine and thin that they did not pick up in the half tone. The little nick at the bottom is the shadow of a part of the test rack. On the other hand, about 80 percent of the faults of the other (at left) focogram do show-they are so gross that a half tone could not help picking them up. There are no lumps and bumps on the Mary Everest mirror-the surface is an optical surface with smooth texture. (We gave such surfaces a name, a year or so ago, but it isn't decorous! The high lights blend into the shadows in a gradual, even transition. The edge is not turned-note the left hand diffraction ring, as per A.T.M 371. The "crest of the doughnut" (A.T.M 262) is in the right place, seven tenths of the distance from center to edge. This mirror would rate as high grade workmanship in any kind of society.

Perhaps no one should set up as a professional, paid refigurer of mirrors "up to any measurable error" who cannot do high grade work; and perhaps, if work really is to be turned out on a buzz saw, at a quoted price which makes high grade work impossible, that fact ought in fairness to the inexperienced seeker of help to be frankly stated beforehand. These comments will also serve, it is hoped, to warn the inexperienced -just the ones who are least likely to sense the same fact-that they should not reasonably expect a high grade refiguring job on a 12-l/2''mirror for 25 dollars, since refiguring a mirror is almost as big a job in some cases as making a new mirror. On the other hand, a pit or two, or a light scratch or two, is not as important a thing to notice as the surface texture ("schoolmarm's leg," if smooth) and the edge-these are the two most important things. By the way, look in vain for the left hand diffraction ring on the middle focogram-or the upper one, for that matter.

We have purposely given no names or identifications in the above, as the motive for publishing these blunt comments is not to hurt anyone but to warn the inexperienced about the fallacy of low-priced services in optics, and perhaps to help keep the general standard of workmanship at a good level.

PROF. C. C. Wylie, astronomer at Iowa State University, Iowa City, Ia., and President of the Midwest Meteor Society, writes that he has been sending observers above the clouds in airplanes to count meteors. "If any of your amateur astronomers have airplanes and could be interested, I will be glad," he adds, "to correspond with them." Here is a chance to die as a true martyr to science-not tamely in bed.

William Tyler Olcott, 62 Church St., Norwich, Conn., author of numerous books on amateur astronomy and one of the founders of the American Association of Variable Star Observers, asks us to announce that any person with a telescope of 3" aperture or larger can engage in the work of the Association, which has a membership of 330. This organization is mainly amateur and its meetings bring together amateurs from many states. No one should feel backward about applying for membership. Another chance to be a (live) martyr.

THE new edition of A.T.M., described elsewhere, contains a chapter emphasizing rigidity in mountings, explaining the principles of getting it, and showing how to make three massive new mountings of solid concrete which Porter, the author labels "Porter's Follies;" also 16 fine new drawings by Porter. Everest's new chapter on HCF is not a revision but an entirely new story, describing his successful technique. Pierce has a brand new chapter on clock drives. The quoted matter on pages 234-240 has been replaced by a full, illustrated treatise on close machine figuring, by Hindle, and the matter on pages 337-343 of the previous edition is replaced by a valuable treatise on the calculation of sidereal time, by the Mayalls of sun-dial fame. About a dozen new notes appear in the Miscellany, also several dozen minor corrections there and elsewhere, and at the end of the book your scribe adds three pages entitled "A Last Word to the Beginner" and winds up with his own immodest picture. This is in answer to numerous requests, but of course nobody will believe this, so go ahead-all you fellers-and tell him he is no shrinking violet and ought to be ashamed of himself!

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