The first is the Lee machine (page 148, "A.T.M."), made by L. St. John Hely, M.D., 912 Macdonald Ave., Richmond, California. The reciprocating rod which leaves the picture at the right hooks up to a reducing gear with single belt drive and the 1/8 horsepower motor of a band-saw outfit. Dr. Hely finds this machine excellent and says anyone can make it who is "enough of a mechanical genius to open a can of oysters."

Leo J. Scanlon of the Astronomical Section of the Academy of Science and Art of Pittsburgh (address Valley View Observatory, 106 Van Buren Street, Observatory P. O., Pittsburgh, Pa.) writes: "I send a picture of a grinding and polishing machine built by Robert H. Marshall, member of our gang. Marshall would sooner spend a week building a machine than a few hours polishing a glass. His address is 120 Maywood Street. The machine is powered with a 1/4 horsepower washing machine motor, on the shaft of which is a worm gear, driving a 20-tooth worm gear, which reduces the speed of the vertical drive shaft to approximately 80 r.p.m. The table is driven at the rate of about 8 r.p.m.

"The grinding arm makes anywhere from 50 to 100 strokes per minute, and is usually run about 80 per minute on a 6-inch glass. The length of stroke can be varied between one and four inches, by suitably inserting a pin in an eccentric arm at the head of the drive shaft. The tool can be made to ride center over center, or can be varied to ride any intermediate zone between center and edge, by adjusting a pin in the bar in the foreground of the picture.

"The grinding or polishing tool is made to rotate either with the mirror or against it, and at various speeds depending upon the surface to be worked. Here's a point that is not generally known," Scanlon continues. "If you revolve the tool with the mirror you deepen the center; if contrary, you cut down the edges. This knowledge is handy in polishing, especially when the mirror doesn't want to clean up around the edges. Parabolizing can be attempted by suitably arranging the cutting speed of the tool by rotating it with the mirror. The tool usually makes 10 to 20 revolutions per minute. Capacity of machine, 12-inch mirror."

DR. K. NAKAMURA of Kwasan Observatory, Yamashina, Kyoto, Japan, writes: "Two photographs are enclosed. One is the view of a large grinding and polishing machine of personal design at my optical workshop in the basement room of the Kwasan Observatory. The machine can polish 30-inch mirror easily. The other is the photograph of 10-inch, f/3.8 photographic reflector belong to Mr. Shibata. The guiding telescope is the four-inch reflector. The optical parts were made by me and the mechanical parts by Nishimura works. The l7th magnitude stars are easily photographed with one hour exposure." Dr. Nakamura sent three photographs, not two as he wrote, the third being that of a machine for grinding mirrors up to 12-inch diameter. There is a lot of amateur telescope-making activity in Japan. We have seen their instruction book but not read it!

J. W. Fecker, professional optician, 2106 Perrysville Avenue, Pittsburgh, Pa., has given us a photograph of a large machine, which is reproduced on the opposite page. This is the type shown in "A.T.M.," page 151, Figure 3, at C, but very much larger. Mr. Fecker states that this machine is used by him for giving a first polish to large surfaces, and that he uses other means for final polishing and figuring.

Edwin P. Martz, Jr., 726 North Elmwood Avenue, Oak Park, Illinois, sends a photograph of his own machine, which is of the same type as the one just mentioned. Martz has three telescopes and is making a special study of Venus, using filters for improving definition.

AMATEUR telescope making and astronomical activities reported are as follows: The Amateur Telescope Makers of Dayton (Ohio) have elected Mr. Loren Shumaker of 1608 Wyoming Street, Dayton, secretary of their organization, which has 25 members. Mr. Shumaker has worked out a method of making the Ronchi test quantitative. Dr. J. A. Anderson of the Mount Wilson Observatory has independently worked out a similar method, and Mr. Franklin B. Wright, 155 Bret Harte Road, Berkeley, California, Chairman of the Eastbay Astronomical Association and co-author of "A.T.M." (pages 257~261), is said to have worked out something similar.

An astronomical society has been organized in New Orleans. Mr. Harry L. Lawton 215 Stella Street, that city, is president.

The Westinghouse Club at Wilkensburg, Pa., has discovered an interest in telescope making and microscopy and has an Optics Section devoted to these hobbies, according to Mr. Fred C. Wilharm, Box 63, Homewood Station, Pittsburgh.

SOME years ago the price of a six-inch mirror made by Zeiss was 150 dollars. Dealers who started in business after the telescope-making hobby was developed among our readers cut this price to about 50 dollars. Partly this was justified by the facts but partly, it is thought, this resulted from a feeling that a maker who was only recently an amateur ought not to charge as much as a professional. Nevertheless many amateurs can do work fully as good as professional work, and better than some that had been sold previously.

More recently all sorts of cheap mirrors have been offered. If you have made mirrors yourself you know that no one can afford to make good mirrors at very low prices. If you have not, be warned and do not take the lowest bid.

Recently a reader wrote us that his eight-inch mirror, refigured by a dealer, would not resolve detail resolved by a six-inch refractor which he had used. We asked him to send it to us. On test the difference in radius of inside and outside zones proved to be a half inch! (f/10 mirror). The dealer had called this mirror paraboloidal. lt was not paraboloidal, nor was its curve even a conic section. If your purchased or refigured mirror seems suspicious we should like to hear from you.

The Society for Amateur Scientists (SAS) is a nonprofit research and educational organization dedicated to helping people enrich their lives by following their passion to take part in scientific adventures of all kinds.