Magic-Paper Fortune Telling
At outdoor carnivals and fairs there is usually a fortune teller who uses a glass wand to cause one’s fortune to appear on a pad of paper. Anyone may perform this trick by observing the following directions.
Instead of a glass wand use a long, narrow bottle of glass. Dip a new pen into copper sulphate, diluted with six parts of water, and write out the “fortune” on a piece of paper. The writing, when dry, will not be visible. Next procure two corks to fit the bottle. An unprepared cork is placed in the bottle and the other is pocketed, after hollowing it out and inserting a small sponge soaked in pure ammonia.
The bottle with the cork is passed out for examination. The cork is casually placed into the pocket after it is returned by a bystander. A pad of paper is then proffered and an initial is placed on the pad of paper by the person whose “fortune” is to be told. The paper is rolled up, with the prepared side on the inside, and inserted into the glass bottle. The fumes of ammonia will develop the mysterious message. The trick can be repeated if several prepared sheets of paper are on hand, and always proves of interest in a party of young persons.
Common Mistakes in Model Making
By H. J. GRAY
Models made as a pastime or for exhibition purposes should represent correctly the full-sized machine, not only as regards general design but also in the proportioning of parts, the finish, and the choice of materials. The satisfaction derived from the possession of a model is greater when it is truly representative. Study and careful measurement of the original are necessary to attain this result, and provide valuable experience in the application of correct mechanical principles.
The most conspicuous, though perhaps not the most frequent, errors made by amateurs are in the proportioning of the various parts. This usually arises from insufficient study of the original machine, and is often sufficiently glaring to attract the attention even of a casual observer. The foundation or base of a model stationary engine, for example, is often painted to resemble brickwork. This is correct, provided the spaces are proportioned so as to represent bricks and not three-ton slabs of granite.
Mistakes are made in the selection of pulley wheels, both as regards the character and the size of the pulley that would be suitable for the particular purpose.
The “cheese-head” or flat-head machine screw appears to have a peculiar fascination for the model maker, judging from the frequency with which it is misplaced. It is only necessary to consider what would happen in a full-sized machine if such screws were used for making joints in valve rods, cylinder covers, slide bars, for fixing bearing caps, and the like, to realize how completely such a defect mars the appearance of a model to a discriminating eye. Bolts, or, in some cases, studs and nuts, should be used to give an appearance of correct workmanship.
Fig. 1
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Fig. 2
Fig. 4
Details of Correct and Incorrect Practice in Model Making: Fig. 1, Valve Rod Joined by “Cheese-Head” Screws, Wrong, and Joined by Joint and Pin; Fig. 2, Bearing Cap Fixed with Flat-Head Machine Screws, Wrong, and with Studs and Nuts; Fig. 3, Cylinder Cover Fixed with Flat-Head Machine Screws, Wrong, and with Studs and Nuts; Fig. 4, Representation of a Brick Foundation, Incorrectly on Side, and Correctly on End
Many novices make a serious mistake in the character of the finish given to the various parts. This usually results through devoting insufficient attention to the method of manufacture adopted in engineering practice. Under the impression that a mottled appearance gives an ornamental effect, they will make a shaft end with a scraped finish. To the casual observer there would be nothing amiss, but a mistake of this kind would offend the trained eye of an engineer, because it is entirely unrepresentative. The object of scraping sliding surfaces is to obtain a greater degree of flatness by removing small inequalities. As the subsequent use of a file would only undo the work of a scraper, the surface is permitted to remain mottled, as left by the scraping tool. But the end of an engine shaft is not a sliding surface, and in engineering practice would be finished in a lathe.
Nickelplating is often resorted to in order to produce a brilliant and supposedly pleasing finish to the model of a casting. This is obviously wrong, for the actual casting—which might weigh tons—would be painted, and not electroplated.
Locomotive wheels or stacks of polished brass add to the appearance of a model only in the eyes of the uninitiated. Few persons would care to risk a railroad journey if the engine had brass wheels. Iron or steel is the correct material to use. Brass is also often used instead of iron for cylinders, connecting rods, and starting levers on models, or for steam pipes, which should be made of steel or copper.
In certain cases there may be unusual difficulties in using the correct material for a machine part made to a small scale. It is then permissible to use other material, provided some attempt is made to disguise the fact by means of an appropriate finish. Copperplating, for example, may be used to disguise some other material, if the parts should properly be made of copper. It is often convenient to make a model boiler of brass. It should not be polished but bronzed, to represent the iron or steel plates of a full-size boiler.