"We call our reproductions 'fossilides,'" write the Higleys. "They were developed as part of a college course on the preparation of biological material for use in elementary schools. The course required the collection and preservation of specimens in a form suitable for subsequent use in classrooms. A number of preserving techniques were demonstrated as examples, including the method of making contact prints of leaves on photographic paper. Such prints are little better than silhouettes, so we decided either to find or develop a method that would preserve the detail of a specimens well as its gross form.

"Plastics seemed to offer interesting possibilities. Leaves could be sandwiched between two sheets of clear plastic and bonded with plastic cement, embedded in liquid resin that would harden bpon exposure to air or bound between strips of adhesive cellophane tape. After a number of experiments the last two methods were dismissed. Results were unsatisfactory because either the materials exhibited poor characteristics or the technique was impractical. The sandwiching method appeared to hold more promise than the others, but at ist only slightly more.

"The specimens were placed between two sheets of plastic that had been coated with cement, and the two sheets were clamped together with a small press. The assembly was then placed in a preheated kitchen oven until the bond formed. During several experiments the cement was omitted so that the minimum temperature and pressure required for uniting sheets of plain acrylic plastic could be observed. In one case the sheets were removed from the oven prematurely and they separated. A faint impression of the specimen, a leaf, had been made in each sheet. The outline and vein structure had been registered in the soft plastic with as much sharpness as one would expect in a leaf print and the plastic impression contained considerably more fine detail!

"The press was simply two pieces of sheet steel 3/16 inch thick, four inches wide and eight inches long. At first the steel plates were pressed together by a "C" clamp but this made them bend.

The difficulty was avoided by drilling holes in the corners of the plates for bolts. This turned out to be a fortunate solution because pressure initially applied by tightening the bolts is relieved as the plastic softens and so the flow of the soft material is automatically limited. Spring clamps that maintained a constant pressure would make the specimen push through the soft sheets.

"Although the impression faithfully reproduced the contours of the specimen, the surfaces of the plastic in contact with the metal plates came out of the press with a frosted texture-a reproduction of the mill finish on the plates. Polished liners were obviously required, so we tried a series of materials, including polished brass, glass and chromium-plated sheet steel polished to a mirror finish. All the materials worked, but metal was more convenient to use than glass, which breaks unless sharp changes in temperature are avoided.

"The initial experiments were made with acrylic plastic, a relatively expensive material. Hence cellulose acetate, a less costly material, was tested. The impressions showed more detail than those made with acrylic but subsequent experiments disclosed several disadvantages. The sheets tend to curl when heated. Vinylite was tried next. It reproduced as much detail as cellulose acetate and remained flat at all temperatures. Finally a friend who is a specialist in plastic vacuum-forming suggested cellulose acetate butyrate and solved the problem. Butyrate records fine detail, remains flat under heat, is easier to cut than Vinylite and does not become brittle or discolored with age.

"Thermoplastics are easily deformed by light pressure when hot, but like all fluids they respond to the forces of surface tension. When the pressure is relieved, some plastics, depending on their temperature, tend to return to their former shape and others to assume the minimum surface-to-volume ratio. This means that pressure must be maintained on the plastic until the press has cooled to room temperature, otherwise the plastic will flow, bubbles may develop and detail will be lost. A large press may require as much as two to four hours to reach room temperature, an impractical interval if a number of impressions are wanted over a weekend if The solution is to cool the press with water. Water must not come in contact with the hot plastic, however, or the] material will turn milky. Some presses, are cast with an internal channel for circulating water, like the motor block of a gasoline engine. Small presses can be fitted with a similar cooling arrangement by soldering to the pressure plates a length of quarter-inch copper tubing bent into a spiral or zigzag pattern. The tubing is connected to a cold-water tap when the assembly is removed from the oven. Construction details can be improvised according to the materials at hand. The sequence of elements in the press pile-up, except for the cooling coils, is shown schematically in the accompanying drawing [Figure 1].

"To produce fossilides of leaves and other relatively thin specimens the experimenter will need sheets of cellulose acetate butyrate in three thicknesses: .015 inch, .02 inch and .03 inch. The plastic can be bought from dealers who specialize in art supplies. The pressure plates should be made of quarter-inch steel plate. Boiler plate is satisfactory and can be procured from garages that service large trucks and from most machine shops. We have discovered that the plates that impart a glossy surface to the plastic can be made of sheet brass, copper or aluminum. The inner surface of tin cans finished with gold-colored lacquer can also be used. The most satisfactory liners, however, are a pair of chromium-plated metal mirrors. One liner must be backed by a cushioning material such as glass-fiber matting or hard rubber to equalize the pressure on the specimen. We prefer hard rubber. If the reproductions are to be projected they should be inserted into slide mounts of appropriate size. Mounts can be bought from dealers in photographic supplies.

"To make the fossilide cut a plastic rectangle a quarter of an inch larger than the desired slide. Assemble the press in the sequence indicated by the schematic drawing, with the side of the specimen to be reproduced in contact with the plastic. Tighten the bolts, but not enough to crush the specimen. Preheat the oven to 210 degrees Fahrenheit, place the press inside and tighten the bolts a half-turn every five minutes for 20 minutes. (If acrylic plastic is used instead. of cellulose acetate butyrate, preheat the oven to 800 degrees F.) Remove the press from the oven, cool and disassemble. Trim the plastic as required for a snug fit with the slide mount and assemble the slide.

"If the impression is generally faint, or faint in some areas, the specimen may not have been in good contact with the plastic. If the specimen was in contact and if the impression is uniformly faint, insufficient pressure was exerted by the press. Try again and tighten the bolts a little more after each five-minute interval. Too much pressure results in grossly distorted impressions. Occasionally excessive pressure also makes a blank spot form in the center of the impression.

"The technique is not without its limitations. Specimens must have some rigidity and enough strength to maintain their shape under the pressure required to deform the heated plastic. Fragility must not be mistaken for lack of rigidity, however. Fragile specimens such as a butterfly wing or a moth's proboscis reproduce beautifully. Flaccid tissue such as raw beef does not yield satisfactory impressions. The hobby of making fossilides tends to be a seasonal activity for the simple reason that interesting specimens are more plentiful during the summer. This may be considered a limitation. On the other hand, some specimens can be dried without injury and processed during winter months. Incidentally, specimens having a high moisture content tend to yield milky slides and must be partially dried.

"Although the slides are clear and transparent, they project as black and white unless colored plastic is used or the impression is dyed. We have experimented with color and find that in general it has little effect except to reduce the brightness of the screen. Interesting color effects can be achieved, however, and may serve some purpose.

"Our collection runs the gamut of the botanical kingdom from simple mosses and lichens through the bark, needles and seeds of coniferous and deciduous trees. Flower petals, stems, roots and stalks reproduce well. Longitudinal sections and cross sections of stems are especially interesting. Leaf impressions constitute the largest category in the collection. Ferns give the most striking impressions. The spore cases show up vividly, as does the structural architecture of the fronds.

"We have selected our zoological specimens with an eye to the rigidity of cellular structure. The collection is dominated by insects. Body details, leg joints and even the compound eye reproduce well. So do spiny-skinned animals, the skeletal portions of fishes, the feet and feathers of birds and the skins of vertebrates such as snakes.

"Teachers at both the secondary and college level who have viewed our collection have stated that it should be a valuable new adjunct to the teaching of biology. The leg of a bumblebee, for example, can be viewed on a screen in three dimensions, showing its joints and the minute projections that serve as pollen catchers. Amateurs who take up this hobby can not only have the fun of assembling a unique and valuable collection but can also experiment with new plastics and perhaps extend the method to specimens that cannot be reproduced with the materials now available."

In June, 1953, this department presented a description of an unusual seismograph made by Elmer Rexin of Milwaukee, Wis. Rexin's device detects earthquake waves by measuring changes in the level of water in a well. Evidently the well is somehow connected to Lake Michigan, because Rexin now reports that his device detects not only earthquake waves but also seiches, the oscillations in the level of a lake that are caused by variations in atmospheric pressure. The effect of earthquakes on ground water is not unknown. In some regions of frequent earthquake activity the ground is dotted with small conical mounds of sand that mark points where water has erupted under the pressure generated by a quake.

Until two years ago, however, the editor of this department had supposed that opportunities for constructing hydroseismographs were confined to a few areas. Now I am not so sure. During the past two years I have heard about the phenomenon in half a dozen states. In 1959, for example, I arranged for a well to be drilled at my house in Pennsylvania's Monroe County. The driller brought in a high-pressure artesian well. A gauge was tapped into the casing at the time the well was capped. A few days later I noticed that the pointer was moving up and down slightly. The afternoon newspapers reported a large earthquake in the Aleutian Islands. The time of the quake and the movement of the gauge matched (when the travel time of the waves was taken into account). Oil-well drillers in Oklahoma City and water-well drillers in Burlington, N. C., Haverhill, Mass., and Omaha, Neb., have made similar observations. Can it be that all subterranean fluid, oil as well as water, responds to seismic waves? Amateurs are uniquely equipped to investigate the question. They are widely distributed geographically and presumably have the time.

An apparatus for recording earthquakes by means of wells has been worked out by Gerald J. Shea of Terre Haute, Ind. He writes: "In the summer of 1954, while fishing in a strip mine pond near Riley, Ind., I saw a variation in the water level of the pit a few seconds before I heard the sound of a very large blast about a mile away. The water level seemed to drop slightly at first and then rise and fall in a series of decaying vibrations. This made me wonder if ground water could be used for detecting elastic waves in the earth. An apparatus for observing the effect could consist of a float linked by a system of amplifying levers to a pen recorder. It was obvious that the open pond could not be used, however, because surface waves stirred up by the wind would be transmitted to the pen and confuse the record. It occurred to me that there would be no 'noise' of this sort in a well, but that the water level in a well might vary in response to elastic waves set up in the earth by blasts. (At this time I had not even thought that a well could react to earthquake waves.)

"The well selected for the experiment had been dug into earth that gradually changed to gravel at the level of the local water table. The well is about three miles west of the center of Terre Haute at 400 feet above sea level. It is 10 feet wide in diameter, 65 feet deep, cased to the top with vitrified brick and cement and is normally half-full of water.

"My initial apparatus consisted of a hollow copper float at one end of a lever that was linked by a wire to a second lever at the surface. The upper lever actuated a recording stylus that made a trace in a smoked cylinder, as shown in the accompanying diagram [Figure 5]. It turned out that the excursions of the stylus overlapped so much that the insertion of time marks was impractical. Later a pen equipped with an ink feed was substituted for the stylus, but capillary attraction between the ink and the paper reduced the sensitivity of the apparatus. The installation, though crude, was worth its cost, because, much to my astonishment, recordings of seventh-magnitude earthquakes at distances up to 4,000 kilometers appeared occasionally. They resembled the records made by the Bosch-Omori and modified Milne-Shaw seismographs. In some respects the well recordings were superior to Bosch-Omori recordings because differences between the three kinds of earthquake waves were more distinct.

"To increase the sensitivity of the apparatus and provide positive control of pen excursion, I replaced the mechanical system with an electric drive. The end of the float lever was fitted with a coil of fine wire that moves in the field of a permanent magnet, as shown in the accompanying drawing [below]. Currents induced in the coil are transmitted to the surface by a pair of leads and amplified to drive a galvanometer recorder. [A similar apparatus is described in The Scientific American Book of Projects for the Amateur Scientist.]

"Changes in water level are amplified about 100 times in terms of pen excursions, and the character of the graph compares well with that of the modified Milne-Shaw seismograph. Surface earthquake waves (S waves) record but do not yield good magnitude determinations. Professional seismograph observatories are equipped with a minimum of three instruments: one for east-west vibrations, one for north-south vibrations and one for vertical vibrations. The water in the well moves vertically. But because water level is determined by forces acting on the water-bearing sand from all directions my recordings are the result of all three motions [see illustration in Figure 7]. Seismographs of this type have no clear-cut advantage over conventional instruments, but they d provide the amateur with an inexpensive means of investigating the fascinating question of whether or not ground water everywhere measurably responds to seismic disturbances."

A red-letter day on the calendar of serious amateur telescope makers is the annual gathering of the clan at "Stellafane," near Springfield, Vt. Hundreds of amateurs, and a few professionals, come from all parts of the U. S., and they are joined by a sprinkling of confreres from abroad. Many veteran telescope makers regularly schedule their vacations to coincide with the conclave, which is an admixture of socializing and high-level telescope talk.

This year, according to James W. Gagan of the Stellafane Committee, the convention will be held on August 12, the first Saturday after the new moon of August 11. Edgar Everhard of Mansfield Center, Conn., will preside. Stanley W. Brower of Plainfield, N.J., will conduct the afternoon session, "Techniques of Polishing and Figuring Glass." Alan Mackintosh of Glen Cove, N.Y., will preside at a meeting of the Maksutov Club at 4:15 p.m. The evening session will be given over to talks by Walter Scott Houston ("Deep Sky Wonders"), Henry Specht ("Photographic Measurements of Variable Stars") and Walter Semerau ("Solar Research"). Many of those in attendance will enter telescopes in the traditional competition for excellence of craftsmanship.

The first Stellafane meeting was held in 1925. Stellafane ("Star Temple") is the observatory of the late Russell W. Porter, the dean of U. S. amateur telescope makers. Present at the meeting were Porter; Albert G. Ingalls, for 28 years the editor of this department; G. N. Bower of the department of astronomy at the Universily of New Hampshire; R. M. Wilson of the U. S. Geological Survey and his assistant R. W. Walton. Also in attendance were O. S. Marshall, Roy Lyon, Frank Whitney, Fred Barber, C. B. Damon, Oscar Fullam, Everett Redfield and John M. Pierce. To the best of our knowledge Fred Barber is the sole surviving charter member.

Bibliography

ELEMENTARY SEISMOLOGY. Charles Francis Richter. W. H. Freeman, 1958.

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