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bing to the wood. Allow time for drying and then rub again, renewing the polishing substance on the waste when necessary by dipping the latter in the two liquids alternately. A very high polish that will not readily scratch is the result

Freezing of Mine Pump

What is the best way to keep a mine pump operated by compressed air from freezing?— C. L. S.

The best method is that which is usually practiced by miners; i. e., the reheating of the compressed air in the mine, close to the pump. The troublesome question of freezing is completely obviated, under ordinary circumstances, and a large gain in efficiency is also secured. Considering the benefits that accrue from this system it may be stated that it is comparatively inexpensive and it is well worth the trouble in advance to avoid the trouble which results from neglect.

Home-Made Screw Driver

Please tell me how to make a screw driver.— T. A. V.

Take an old file some eight inches long and grind it smooth on sides and edges

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Place the rubber on the leak with the steel plate on top; then screw the clamp on tight.

Flame Tells Temperature

1. Can the temperature of a fire be told by the color of the flame?

2. 'How is the surface of a chimney acted on by a gale of wind found?—W. M.

1. The following table may be used for approximating temperature at a glance; where accitracy is required, calorimeter tests should be resorted to for temperature.

Faint red indicates about.. 960° Fahr.

Dull red ""..1290°"

Brilliant red ". .1470°"

Cherry red ". 1650J

Bright cherry red" "..1830°"

Dull orange " ". .2010° ■"

Bright orange " ". .2190°"

White hear " "..2370°"

Bright white " ". .2550°"

Brilliant white" ". .2730°"

2. For wind pressure the effective section of round and octagon chimneys and chimneys of more than eight sides are taken as one-half the actual diametrical section. Thus, if a chimney has a mean diameter of seven feet and a height of 100 feet, the diametrical section would be 7 times 100 = 700 square feet, of which 350 square feet is regarded as the effective surface acted upon by a gale of wind. For square chimneys, the effective section is taken as the actual diametrical section, from which it will be seen that a square chimney presents twjee the surface for wind pressure as does an octagon or round chimney, the mean diameter of which is equal to the length of side of square chimney, the height being the same.

Automatic Fire Alarm

I have heard that an instrument can be installed in buildings which will automatically give an alarm by electricity when the building takes fire; if so, would you please give me a description of its operation ?—H. C. H.

The accompanying figure will illustrate the principle upon which a metallic thermostat operates. This thermostat is one

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Automatic Fire Alarm.

type of instrument which is installed in buildings to give an alarm when the building takes fire. Each of the U shaped metallic strips are built up of a copper strip, and a zinc strip soldered together. One set of strips is thick, and the other thin. They are of the same length. The zinc strips are placed on the inside as shown by the sketch. A rise in temperature causes the plates to be heated and to expand. Unequal expansion of the two arms of the U, causes a tendency to separate, but as one is fixed, the whole effort is extended to the second arm. The plate B which is smaller, absorbs heat more readily, so that if increase is sudden and of a large amount, as is usual at the beginning of a fire, it expands rapidly and makes contact with A through points C and C. A being of greater bulk, takes longer to heat and expand. If the air becomes heated from ordinary causes, the rise in temperature always being more gradual, the plate A has time to expand, and the two contact points C and C do net touch. These contacts are made of bent silver or platinum strips, so that contact may take place in all positions of the plates. When the strips C C touch, it closes an electric circuit which rings a bell, this bell being located at the point where the alarm of fire is desired. The particular advantage of this type of instrument lies in its automatic action for preventing false alarms.

Removing Rust from Iron

How can rust be removed from iron?— A. L. W.

A method of removing rust from iron consists in immersing the articles in a bath consisting of nearly saturated solution of chloride of tin. The length of time during which the objects are allowed to remain in the bath depends on the thickness of the coating of rust; but in ordinary cases twelve to twenty-four hours is sufficient. The solution ought not to contain a great excess of acid if the iron itself is not to be attacked. On taking them from the bath, the articles are rinsed in water and afterward in ammonia. The iron, when thus treated, has the appearance of dull silver; but a simple polishing will give it its normal appearance.

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TBnaft Diviniin\g'=Rodl Problem

By K>b% Alfred Griradesrawitz

Berlin Correspondent Technical World Magazine

^/?TTA /tfN an article published in a rvgw recent issue of The Tecii

/lli! Nical World Magazine, «f« tne wr'ter described some

<glw experiments recently made

"W^TiLx^a jn Germany in connection with divining rods.

Owing to the criticism and discussion aroused by this article, the following further particulars would seem not to be out of place:

It may be said that most of the unfavorable criticism made on the above problem is based merely on the assertion that the alleged working of the divining rod not being accounted for on known physical laws, the whole matter should not be considered worth a scientific discussion. How unscientific this method is need hardly be pointed out. In fact, so many novel phenomena which could not have been explained by the laws of nature with which the physicist of say twenty years ago was acquainted, have been made known in the course of the last few years that the imprudence of a priori rejecting any enigmatical phenomenon is self evident.

Certain scientists, on the other hand, having tried the divining r id, and having been unable to confin i its alleged working, considered their failure as proof against these phenomena.

Now as expressly stated in the writer's article, these phenomena are distinctly subjective, that is, depending on a certain personal disposition which is not possessed by everybody.

The writer recently communicated with Herr von Biilow-Bothkamp, whose experiments with divining rods have been described in the article referred to, and requested him to demonstrate before him the phenomena in question.

The scientist willingly acquiesced to this demand and during the next session of the Prussian Lower House of Parlia

ment invited the writer to attend a demonstration in the building of the Prussian Parliament.

The first thing that Herr Biilow did after the writer's arrival was to touch his hand in order to ascertain whether he was possessed with the peculiar disposition necessary for performing the divining rod phenomena. After having answered this in the affirmative he at first demonstrated the working of an iron rod kept with a certain tension in his hands whenever this was carried along above a silver or gold coin placed on the table.

As soon as the rod passed the spot in question a violent deflection (which according to the personal disposition is directed either upwards or downwards) was observed. Herr von Biilow next began walking along the corridor with his rod in his hands when a lively deflection was observed at certain places. The writer repeated these experiments, and was able likewise to find such a deflection at about the saTne points as the experimenter, and which correspond to the beginning and end respectively of an underground water vein.

Herr von Biilow even calculated the depth of the latter. He also told the writer his experience as to a supposed influence exerted by underground springs on the sleep of man. He firmly believes (and has confirmed in the case of many persons) that whenever a bed is placed on the top of an underground spring and in the direction of the latter, the sleep of any somewhat susceptible individual is bound to be a troubled one.

It should also be remembered that the German Emperor has sent Herr von Uslar to the German South West African Colonies, and that according to recent newspaper report this experimenter has been surprisingly successful in finding out hundreds of underground springs. The importance of such work for colonization purposes need hardly be pointed out.

It will be interesting in this connection to refer to an observation made as far back as in 1747 by a German experimenter, that a luminous emanation of variable shape will appear in the dark at points on the surface of the earth below which there are extensive ore deposits.

Immediately before or during a thunderstorm these phenomena are said to become specially striking.' Similar observations have been made more recently in North America in the neighborhood of ore deposits. Though much should be ascribed to superstition and to errors of observation, the fact nevertheless has been confirmed by recent investigation. The electric emanation given off from the surface of the earth has in fact been repeatedly ascertained by means of photography. Mr. K. Zenger used in this connection photographic plates impregnated with fluorescent substances. It may thus be taken for granted that the emanations in question occur with a specially high intensity at those points of

the ground where good conductors of electricity are found in large amounts in the neighborhood of the surface of the earth, that is to say, above ore deposits, most ores being very good conductors of the electric current. Brown coal, mineral coal, especially when containing pyrites, as well as anthracite, are fairly good conductors. The difference in the intensity of radiation as compared with points free from ore would seem to be recognized by means of photography, thus affording to geologists a rather simple means of locating ore and even coal deposits liable to be worked. The mining work in a pit would also be facilitated to a high extent by a similar process, as in the case of a sudden discontinuance of ore-carrying veins, the nearest deposits would be found out without any difficulty.

Attempts to utilize this method for practical purposes are being made by Professor H. Barvir and Mr. Zenger of Prague. The invention of an objective method of water finding by Mr. Adolf Schmidt of Berne. Switzerland, finally was also mentioned in the writer's previous article.

An Up»to»Date Substation

By R. F. Perry

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3 N example of the electric substation that is rapidly superseding the old independent power houses is that of the Newton and Watertown Gas Light Company, which has just completed its first year of operation in a suburb of Boston. Located in a city where architectural beauty is insisted upon, the new structure is of concrete, with brick trimmings and red tile roof, the whole an influential element in the raising of the standard of municipal architecture. The building is fireproof throughout and remarkably up-to-date in design and equipment.

The current is transmitted by two three-phase, 6,900-volt circuits from the

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Commonwealth Avenue Boulevard. The overhead line is of bare stranded aluminum cable equivalent to No. 0 copper. There is a second tie-line through Dedham and Needham to the station to use in case of accident to the shorter line.

Three 50 K. W. oilcooled transformers are used for the small day load, stepping the voltage down to 2.300 volts for local distribution, and in mid-afternoon, when the load increases, three 200 K. W. and one 500 K. W. aircooled transformers relieve them until toward morning when the load has dropped again. These transformers stand on a cement platform over a pit (there is no basement to the building) and a thirty-six-inch blower direct connected to a small motor furnishes the air draft. The one 500 K. W. unit is a recent addition to the original station equipment, necessitated by the unforeseen increase of commercial load. Four sixty-light tub transformers with their switchboards for the arc lights occupy one side of the building.

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Switchboard In The Model Substation Of The Newton & Watertown Co.

The feeder switchboard with its oil switches, recording and indicating meters, time limit relays and other safety devices, is on one side of the bank of transformers and the distribution board on the other.

Every means for safely manipulating, controlling and recording both the 6,900 volt current and the 2,300 volt is installed. All connections are through ducts under the floor and switchboard fittings are carefully protected.

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