BEGINNING with the present issue this department of SCIENTIFIC AMERICAN is extending its coverage to include the work of amateurs in all departments of science. Information on telescope making and amateur astronomy will continue to appear here regularly, as it has for nearly 27 years. But in addition the department will report the work and adventures of investigators in the many other branches of science in which amateurs are active. We invite all those who find relaxation in the study of nature, directly or vicariously, to share these pages.

No one knows just how many U. S. citizens spend all or part of their leisure in scientific study and experiment. One thing is sure: the awesome setup of modern science, with its million-dollar cyclotrons and billion-dollar research centers, has by no means frightened amateurs off the scene. Not long ago the American Philosophical Society made a study, financed by the Carnegie Corporation, of adult education in science in Philadelphia, the onetime home of one of the nation's great amateur scientists- Benjamin Franklin. W. Stephen Thomas, who conducted the survey, had no trouble in compiling a list of more than 8,000 laymen in that city who were actively interested in science. Of these no fewer than 700 had made contributions to knowledge important enough to merit professional attention. These citizens of multifarious workaday occupations-dancers, lawyers, housewives, loom fixers, plasterers, bankers, X-ray repairmen, advertising men-were probing a range of scientific subjects that extended from the atom's nucleus to the visible boundaries of the universe.

The study also turned up the interesting fact that in Philadelphia there were 200 science clubs with national affiliations. Judging from the membership enrollments in some representative national societies, it seems safe to say that the number of scientific-minded laymen in the U. S. runs into the hundreds of thousands.

The collective contributions of amateur workers to science and technology are not trivial. The story of the achievements by amateur telescope makers in making roof prisms and other precision optical parts for the Navy during World War II is well known. For years the U. S. Weather Bureau has depended on the observations of some 3,000 well-organized amateur meteorologists. Still other groups cooperate with professional scientists in observing bird migrations and populations, radio disturbances in the ionosphere, the behavior of variable stars, earth tremors, soil erosion and so on. It was an amateur who discovered the planet Pluto, and an amateur who played a leading part in the development of vitamin B.

The amateur is generally a fellow of boundless curiosity who enjoys digging for facts-and sharing them with everyone he knows. It is not the hope of epic discoveries that keeps him at his avocation. If he should chance to learn something important to mankind, that would indeed be a thrill, but he finds reward enough in the fun of the free quest.

TO FIND a happy amateur, as good a place as any to start is in the basement of a cottage at Elma, N. Y. There, in a tiny corner cubicle that looks like a photographer's darkroom, is one of the most interesting seismological stations in the U. S. It is owned and operated by Harry H. Larkin, Jr., who during business hours is vice president of Larkin Warehouse, Inc., in nearby Buffalo. An amateur meteorologist and seismologist, Mr. Larkin is a cooperative observer for two branches of the U. S. Government. He makes regular weather reports to the U. S. Weather Bureau, and whenever his instruments record an earthquake, he dispatches his readings by teletype to the U. S. Coast and Geodetic Survey. Mr. Larkin's special interest in seismology is the study of microseisms, the constant tiny tremors of the earth that seem to link the planet's structure with its weather but are still an unsolved puzzle ("Microseisms," by L. Don Leet; SCIENTIFIC AMERICAN, February, 1949 ) .

The earth sciences have fascinated Mr. Larkin for as long as he can remember. As a boy he used to visit every weather station within range of the family car with his father. Later, after taking up flying, he began his career as a meteorologist by installing a barograph in the Larkin den. Today his back yard bristles with rain gauges, thermometer shelters, towers supporting anemometers, wind vanes, sunshine recorders, time-lapse sky cameras-a full complement of professional instruments. Two years ago Mr. Larkin's growing reputation as a cooperative weather observer prompted a professional seismologist to invite him to help in the investigation of microseisms. Mr. Larkin added two sheets of recording paper to the daily dozen already coming off his instruments and embarked hesitantly on what has since become an absorbing and Often thrilling experience. As he puts it, "I entered seismology through the back door and can perhaps be described best as an amateur meteorologist with seismology as a hobby, or vice versa."

Practically everything a seismologist knows comes from the interpretation of wavy lines traced on a sheet of paper, and to understand seismology one must first understand the instrument that makes this record. The heart of the seismometer is a pendulum, which serves as the sensing element. Its movement records the strength and character of each tremor of the earth. The standard Weichert seismometer of the professionals is a complicated affair with a 175-pound pendulum and a stone foundation extending down to bedrock. But the instrument in Mr. Larkin's basement is astonishingly simple (see drawing at left). On a slab of concrete embedded two feet deep in clay beneath the basement floor stand two slender, upright cylinders: one to measure earth movements in the east-west direction, the other, north-south. Inside each cylinder is a taut vertical wire with a small copper vane attached to it. The vane is the "pendulum," though it extends out horizontally from the wire, instead of hanging. When the earth trembles, the vane swings slightly. A beam of light, reflected from a mirror on the vane, makes a tracing of this movement on a roll of photographic paper wrapped around a slowly rotating drum. In essence, that's all there is to it.

This instrument is known as a torsional seismometer. It is comparatively inexpensive and can be bought in kit form and assembled in a few hours by any amateur. The apparatus was made available commercially about two years ago by the late William F. Sprengnether Jr., president of the Sprengnether Instrument Company of St. Louis. Says Mr. Larkin: "Mr. Sprengnether, an advanced amateur astronomer and telescope maker, wished to encourage amateur interest in seismology and in placing this equipment on the market ignored the conventional profit motive."

Mr. Larkin describes the instrument as follows:

"The sensing element consists of a copper vane about a quarter-inch wide and an inch and a half high, attached along one edge to a hairlike wire held taut by a vertical framework. When earthquake waves or other tremors move the assembly back and forth, the vane rotates in precise response. The swinging of the vane twists the wire slightly which accounts for the name 'torsional' seismometer.

"A small mirror with a focal length of one meter is cemented to the vane. A light beam reflected from it, acting as an optical lever, amplifies the vane's movements and registers them on photographic paper carried by the recorder.

"The recorder is simply a metal box containing a drum to carry the photographic paper. Driven by a small synchronous motor, the drum revolves at the rate of one revolution in 30 minutes and also moves along its axis. Thus the light beam makes a spiral trace on the record sheet. The beam comes from a small lamp in a tubular housing attached to the front of the recorder. At regular intervals the time is marked automatically on the record sheet. These marks were originally made by means of an electric clock, but I have been fortunate in obtaining an International Business Machines master clock which now provides really accurate time control.

"The cost of a single instrument, including material for a room and pier but not providing for an accurate clock, should not be much over $200. This figure will yield, more or less, to the amateur's ingenuity and patience. The cost of photographic paper will run around $25 per year."

At this point it seems appropriate to ask: How does seismology pay off as an avocation? How much fun and action do you get for your money?

Microseisms, tracing their patterns on the sheet hour after hour and day after day, are an endlessly diverting show, and the study of these tremors alone is an undertaking that well justifies building a station. Some microseisms record the tiny shakings of the earth by storms at sea. Some appear to be associated with low pressure systems in the atmosphere. Some come in harmonious groups from no-one-knows-where. Some appear fixed, as standing waves. Others crisscross in random array. The pattern is ever-changing: waves that herald tomorrow's weather, waves that record the onward travel of yesterday's cold front, perhaps even waves that still reflect the earth's dying response to an ice age long past.

But the greatest thrill is to catch the dramatic reverberations of an earthquake, sometimes from far across the globe. Three kinds of waves record this happening. The first is the P or pressure wave, a compressional wave like that of sound, in which the wave motion is in the direction of the waves' travel. The next is the S or shake wave, which vibrates at right angles to the waves' path. Finally there is a long L wave, undulating like a water wave, which journeys around the surface of the earth.

The three waves travel at different speeds. An earthquake is heralded by the sudden appearance on the seismometer scroll of the harsh jagged pattern of P waves, which speed through the earth at five miles per second. After a minute or so, depending on how far the quake is from the station, the P waves begin to die. But the show is far from over. Soon the slower S waves (three miles per second) arrive, as abruptly and violently as the first. They mark a very different pattern, easily distinguishable from the P. Some time later, again depending on the distance of the quake from the station, come the lazy, snakelike L waves (two and a half miles per second) that close the show. The difference in speed between P and S waves makes it a simple matter to determine from a travel-time chart the distance they have traveled and the time when the quake occurred.

Time and distance data provide clues to the structure of the earth. The waves are reflected by its layers of differing material; some of them literally bounce around inside the earth. The reflected waves, differing slightly from those that travel directly to the station, tell something about the depth of these layers. Furthermore, S waves are not detectable at a distance of more than 7,000 miles, indicating that they are blocked somewhere in the depths of the earth. Since S waves can travel only through a solid, this suggests that the earth has a liquid core. The core also slows the passage of P waves; those that have passed through the core are designated P'.

Most earthquakes originate in the outer crust of the earth, but shocks from levels all the way down to about 400 miles have been recorded. Deep-focus earthquakes are recognized by the absence of L waves and the presence of wave trains which have been reflected from the surface above.

Seismologists estimate that about one million true quakes shake the earth each year, and of these something like 150,000 are strong enough to be felt. The magnitude of earthquakes is measured by a scale based on the height to which the pen or light beam of a standard instrument will swing when a quake occurs at a specified distance from the station. On this scale a great shock such as the Japanese quake in December, 1946, has a magnitude of about 8.6; an atomic explosion may produce a quake rated at 5.5, and a mild quake that causes dishes to rattle in the vicinity of the quake center has a magnitude of 2.5.

Earthquakes of course are sporadic and unpredictable. Mr. Larkin's seismometer has recorded two or three major shocks in a single day, while at times several weeks or more pass without a large one. On the average his station registers about one major quake every five days.

The U. S. Coast and Geodetic Survey, with the cooperation of Science Service and the Jesuit Seismological Association, mails out cards after each major earthquake giving the "epicenter" (source) and time of origin of the quake. Any amateur who operates a seismological station as a cooperative observer may get on the mailing list to receive the cards by writing to the Survey. With this information and travel-time charts, it is an easy matter to review seismograph records and become proficient in interpreting them.

By analyzing the wave motion of light, man has solved riddles of celestial mechanics lying billions of miles beyond the trembling surface on which he dwells. But the earth waves, which might tell us a great deal about our own planet, have been comparatively neglected. Do mountain-building convection currents flow within the earth's plastic core? Is that core plastic, liquid-or neither? Although the seismograph was invented 110 years ago, science has yet to resolve these and related questions. Seismologists would like to have many additional workers and a closely spaced network of observing points to supplement the fewer than three score stations now thinly distributed over the North American continent.

Here is a frontier awaiting exploration, one in which the professional geophysicist eagerly invites the amateur's help. Father Joseph Lynch, S.J., head of Fordham University's seismological observatory, has said: "There is a seismological job to suit everyone's purse and everyone's ability-there is seismic work for all-but no financial remuneration." That, indeed, would seem to qualify seismology as an amateur pursuit.

SEVERAL years ago Horace E. Dall of 166 Stockingstone Road, Luton, Bedfordshire, England, built the remarkably compact terrestrial and astronomical telescope shown in Roger Hayward's drawing (left). It is a modified Cassegrainian of 3-1/4 inch diameter, mounted mainly on light aluminum and duralumin parts. It weighs only eight ounces, and can be folded so flat that it juts no farther out of a vest pocket than a fat fountain pen. It gives erect images, and the magnification is continuously variable (pancratic) from 35X to 80X by pulling out the eyepiece. Dall found it a treasure for either day or night use. It has a better light grasp than a three-inch refractor and resolves stars down to Dawes' limit.

Starting from Dall's specifications for diameters, distances, ratios and radii, as shown in the drawing, Frank McCown of Holtville, Calif., has built a similar telescope of four-inch diameter, still small enough to be carried disassembled in a thin 8- by l5-inch box. In the drawing (right), McCown's mounting is shown, for convenience with polar axis vertical. The polar axis is the little stub projecting from a 90-degree angled member in the lower left-hand corner. When this is pointed at the Pole Star in the direction N by adjusting that member, the mounting becomes equatorial.

"This little portable four-inch instrument has performed so well," McCown writes, "as to retire a more cumbersome six-inch Newtonian reflector."

Dall's specifications are shown instead of McCown's so that other builders can work directly from the originals, choosing their own desired sizes. It is sound optics to alter the size of a telescope by reducing or enlarging all measurements by the same proportion. (Preferably not including the indexes of refraction, dispersion and density, or the type number from the glass manufacturer's list.)

The telescope is a modified Cassegrainian of the Dall-Kirkham type with spherical secondary and near-ellipsoidal primary mirrors. The finicky job of figuring the little hyperboloidal secondary of the straight Cassegrainian is eliminated; this advantage is why the Dall-Kirkham is supplanting the old-fashioned type. Design data for the Dall-Kirkham were rounded up and elucidated in the September, 1951, issue of SCIENTIFIC AMERICAN. Dall figured the primary, an ellipse of eccentricity .873, by the direct focal test that was described in Amateur Telescope Making and further elucidated in the last issue of this magazine by Kirkham.

Just as the Dall-Kirkham is a modification of the Cassegrainian, so Dall's own telescopes are a further modification of the Dall-Kirkham. The modification of the modification which might be called the Dall Cassegrainian, and which Dall regards as a most valuable addition to the spherical secondary, is the placing of an erecting lens between the primary and secondary mirrors.

Some years ago Dall made a 15-1/2 inch telescope of this kind and listed the rewards from adding the little erector. It enables the sky-flooding diaphragm to be moved from the eyepoint (where it is an infernal nuisance, having to be fitted to each eyepiece and impossible to keep adjusted because its aperture is so small) to a position between the erecting lens and the eyepiece, where it is out of the way. It has a large aperture, and therefore is easier to keep aligned. It permits the use of wide-field eyepieces with comfortable eyepoint, greatly appreciated by spectacled observers. An iris diaphragm can be used for the sky stop, permitting the aperture of the telescope to be varied by a lever from full to nothing during observation. The long focus of the Cassegrainian can be shortened. Variability of lens-to-secondary and lens-to-eyepiece distance gives a final image varying in angular aperture (on the 155-inch) from f/10.5 to f/25, permitting continuously varying power from 1 to 25 for each eyepiece. And the final image is erect.

Dall designed and built cemented triplet erectors for his two telescopes. The one for the 3-1/4 inch gives uniform zonal focus at mean cone focus 1.23 inch, with .62-inch diameter. The focal ratio of the 3-1/4 inch is variable from 7.5 to 18. As an avocation Dall makes eyepieces and refigures telescope, microscope and camera objectives, his vocation being research in fluid dynamics. A recent book, Some Aspects of Fluid Flow, contains his contribution to the Institute of Physics on fluid flow in orifices, nozzles and Venturi tubes.

In Fundamentals of Optical Engineering Donald H. Jacobs briefly discusses the triplet form of erecting lens and mentions the preference of the British for it. The symmetrical, two-doublet form is more commonly used in the U. S. Data for designing two-doublet erectors were given in this department in March 1951 (where the denominators 2, 2, in equation 5 should be deleted). McCown escaped this problem by making a two-doublet erector out of coated lenses from a war-surplus collection. His erector's combined focal length is 1.9 inch. He found it satisfactory, especially since less than its full aperture is used.

"I am enthusiastic about the Dall erecting telescope," McCown writes, "as the erector serves the purpose of a Barlow lens, also making possible a smaller secondary. The self-collimating feature of the centrally supported mirror has been successful. The threaded ring on the large eyepiece-erector tube screws against a cork ring at the back of the mirror and holds everything in alignment. Once it is collimated, no flare is visible even after repeated takedowns.

"My midget slow-motion mounting is far from perfect. The rods interfere with one another in some positions, but this can be quickly remedied by reversing the base. All but a small part of the sky is accessible. The pressure springs have enough give to allow either rod to be pushed out of gear for a change of view."

In the tubeless telescope, fogging of the mirrors from the observer's breath may be avoided by selecting only breathless views. In McCown's case, which may be unique, this is facilitated by the fact that his farm is below sea level in the Salton Sea depression, so that the instrument is a submarine telescope.

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.