F. Moore, 1021 Pemberton Road, Victoria, B. C., Canada, sends in three photographs, one showing two friends and himself with several interesting exhibits of machine work as added scenic features. Mr. Moore is rather short on words-all he writes is: "I enclose photos of a grinding machine I have constructed. On it an 11-inch speculum is being completed. The 2-1/2-inch achromatic object glass for the finder and the lenses for the eyepieces were also made on it." Evidently Moore and his friends have been making something quite elaborate in the way of a telescope short of a 200-inch. We hope they will some day favor us with a picture of the complete job.

MR. FRANK G. MILLIGAN, 715 . Ravenna Road, Seattle, Washington writes as follows: "Enclosed you will find photographs of a vertical grinding lathe I built for grinding and polishing my eyepiece lens and prisms. The main gear wheel is eight inches in diameter with 50 teeth, and there are two screw threads on the worm. The bearings are made of steam fittings. Three bearings are made of 1-1/2 inch by 3/4 inch pipe crosses. The main bearing for the vertical shaft is made of a 3 inch floor flange, with a close nipple sawed in half and screwed into the flange.

In the nipple is set a small ball bearing embedded in babbit metal, and the end of the shaft is turned down to fit into the ball bearing. The upper end of the shaft is turned to a cone to fit the grinding flat. The vertical shaft is 8-1/2 inches long, and the horizontal shaft carrying the screw is 12 inches long. Both shafts are made of one inch cold rolled shafting. I picked up the gear and worm in a second-hand machinery depot. The motor runs at 1750 r.p.m. The drive pulley is 2 inches, and the driven pulley is 4 inches, in diameter. The main gear makes 35 r.p.m. and reversing the pulleys gives 140 r.p.m. The vertical lathes used by opticians grinding eye-glass lens run 940 r.p.m.

DR. K. NAKAMURA (see "A. T. M.," page 225, at bottom) of the Astronomical Observatory of the Kyoto Imperial University, Kyoto, Japan, writes "The new edition of 'Amateur Telescope Making' reached me safely. I find the book is nearly completely perfected and now the best book of its kind. I feel interest to find my words on page 226. Since the August of 1926, there are thousands of mirror workers in Japan. Most of them were young students of 'teens age, which seems to be somewhat different compared with most American workers.

"I have enclosed a print of my grinding and polishing machine. The original design of this machine was by Mr. Hindle and appeared in English Mechanics, 1923. The machine is simple and easy to construct. It has some defect of producing hill at the center of the mirror, but nearly spherical surface is easily attained when the pitch condition is perfect. But the figuring must be done by hand. I am now working on my 130th mirror."

To this the editor replied, inquiring whether it might be thought advisable to advertise "A. T. M." in Japan. Some weeks later the following answer was received:

"Thank you for your kind letter. There is a book written about the mirror making by Mr. Yamasaki, published in 1926. I have written one recently which is expected to be published in next May. But some of the Japanese amateurs are requesting good foreign book. Therefore you can increase its sale. The Maruzien Company is the best and largest shop of foreign books.

"The Hindle's grinding and polishing machine is a good one but it still requires improvement. It is similar in principle to Ritehey's machine but is improved. My present one is one third dimension of original design. But I am now determined to make double sized one.I wish to add interchangeable straight stroke. I have recently polished several convex surfaces of object glass, with unexpected success. Although good surfaces depend on the best pitch, the interference test proved good spherical surface free from zones, without figuring.

"I start here for Sumatra on March 24 for the observation of total eclipse."

AMATEURS who like to experiment may try out the suggestion contained in Porter's sketch, which we reproduce, of a "dingbat" for applying pressure to a mirror during grinding. The Tel. Ed. first picked up the idea from watching a Chinese laundryman who was using a similar rig "for pressee hardee on shirtee." It consisted simply of a six foot vertical pole with a spring at the top attached to the ceiling, and a point at the bottom. This engaged with a depression in the flat-iron. The idea was sent to Porter who elaborated it as shown, saying he would try it out. Just then he was given a chance to try out something rather more important, as we all know, in California, and therefore it is hoped that someone else will try this stunt and report (1) whether it works, (2) whether it results in any net gain in time and temper.

IN addition to amateur telescope making there is another amateur hobby, at present undeveloped, which it is hoped may some day be taken up and if possible popularized in the SCIENITIFIC AMERICAN. That is, seismology. Several seismologists have expressed interest in the suggestion that amateurs be encouraged to construct inexpensive apparatus for recording earthquakes. In addition to genuine 'quakes there are other interesting local disturbances due to automobile traffic, blasting, railroads, vibrating factories, and so on As Dr. T. A. Jaggar, volcanologist at the Hawaiian Volcano Observatory of the United States Geological Survey, states, "To record every car that passes, its weight and speed, would be quite possible with a seismograph. As to making an instrument for 50 dollars or less, that would be easy for a mechanic." A simple instrument has been described in one of the scientific journals.

At present there is no textbook on seismology suitable for the amateur, Hobbs' being rather old and Davison's being elusive in treatment. However, a noted seismologist is known to have a text book in preparation. Seismology as a hobby-in fact, any other hobby we know of which is suitable for readers of a scientific journal-could hardly compete with amateur telescope making; and the latter will not be dropped until there are signs that its hold is weakening-which certainly is not yet. Several have suggested that a special department of this journal be regularly devoted to all kinds of hobbies. This would possibly prove interesting, but where is the many-sided editor who is to run such a department and where would the line be drawn? The number of hobbies is almost infinite.

How many readers of this journal would take an interest in amateur seismology and will write in to say so?-A. G. I., Tel. Ed.

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.