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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.

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Freezing of Mine Pump
What is the best way to keep a mine pump
operated by compressed air from freezing ?-
C.L. S.

Tools to REPAIR LEAKY PIPE.
The best method is that which is usu-

cticed by miners : ie the re- Place the rubber on the leak with the heating of the compressed air in the steel plate on top; then screw the clamp mine, close to the pump. The trouble- on tight. some question of freezing is completely obviated, under ordinary circumstances, and a large gain in efficiency is also se

Flame Tells Temperature cured. Considering the benefits that ac 1. Can the temperature of a fire be told by crue from this system it may be stated the color of the flame? that it is comparatively inexpensive and

2. 'How is the surface of a chimney acted it is well worth the trouble in advance

on by a gale of wind found ?—W. M. to avoid the trouble which results from

1. The following table may be used neglect.

for approximating temperature at a glance; where accuracy is required,

calorimeter tests should be resorted to for Home-Made Screw Driver temperature. Please tell me how to make a screw driver.

Faint red

indicates about.. 960° Fahr. T. A. V.

Dull red
Brilliant red

...1470° Take an old file some eight inches long Cherry red

.. 1650° and grind it smooth on sides and edges

Bright cherry red

..1830° Dull orange

..2010° Bright orange

..2190° White heat

..2370° Bright white

..2550 " Brilliant white

" ..2730° "

2. For wind pressure the effective HOME-MADE SCREW DRIVER.

section of round and octagon chimneys

and chimneys of more than eight sides are to shape of screw driver. The illustra

taken as one-half the actual diametrical tion shows how it will look when finished.

section. Thus, if a chimney has a mean diameter of seven feet and a height of 100

feet, the diametrical section would be 7 Repairing Leaky Pipe

times 100=700 square feet, of which 350

square feet is regarded as the effective I should like to know how to quickly repair surface acted upon by a gale of wind. a leaky pipe.-A. C. R.

For square chimneys, the effective secSecure clamps of the kind shown in tion is taken as the actual diametrical the drawing. These can be made so as section, from which it will be seen that a to take three or four different sizes of square chimney presents twice the surpipe. Rubber gaskets and small sheet face for wind pressure as does an octasteel plates must be used in connection gon or round chimney, the mean diameThese plates and gaskets must be one ter of which is equal to the length of inch square and one-eighth inch thick. side of square chimney, the height being The plate should be bent to fit the pipe. the same.

Copper

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Automatic Fire Alarm

Removing Rust from Iron I have heard that an instrument can be in- How can rust be removed from iron ?stalled in buildings which will automatically A. L. W. give an alarm by electricity when the building takes fire; if so, would you please give me a A method of removing rust from iron description of its operation ?-H. C. H.

consists in immersing the articles in a The accompanying figure will illustrate bath consisting of nearly saturated sothe principle upon which a metallic ther- lution of chloride of tin. The length mostat operates. This thermostat is one of time during which the objects

are allowed to remain in the bath depends on

the thickness of the coato Zinc

ing 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 AUTOMATIC FIRE ALARM.

be attacked. On taking

them from the bath, the type of instrument which is installed in articles are rinsed in water and afterbuildings to give an alarm when the ward in ammonia. The iron, when thus building takes fire. Each of the U treated, has the appearance of dull silver ; shaped metallic strips are built up of a but a simple polishing will give it its copper strip, and a zinc strip soldered to normal appearance. gether. One set of strips is thick, and the other thin. They are of the same length. The zinc strips are placed on the

Making an Electroscope inside as shown by the sketch. A rise in

Can you suggest how to make a very simtemperature causes the plates to be

ple electroscope, entirely for the purpose of

experimentation ?-M. D. C. heated and to expand. Unequal expansion

Take an ordinary needle, a piece of of the two arms of the U, causes a ten

cork, and a sheet of writing paper. From dency to separate, but as one is fixed,

the paper cut a small arrow. Push the the whole effort is extended to the second

needle into the cork, and balance the ararm. The plate B which is smaller, ab

row on top. Your instrument is ready sorbs heat more readily, so that if in

for work. Next take another piece of crease is sudden and of a large amount,

paper, heat it over a lamp or stove, and as is usual at the beginning of a fire, it

rub vigorously with a bit of woolen 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 nct 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

HOME-MADE ELECTROSCOPE. of this type of instrument lies in its au- cloth or felt. If the paper so treated is tomatic action for preventing false brought near the arrow it will turn with alarms.

the paper, as it is moved back and forth.

That Divining-Rod Problem

By Dr. Alfred Gradenwitz

Berlin Correspondent Technical World Magazine

N an article published in a ment invited the writer to attend a dem83 recent issue of The TECII- onstration in the building of the Prussian

NICAL WORLD MAGAZINE, Parliament.

in the writer described some The first thing that Herr Bülow did

be experiments recently made after the writer's arrival was to touch B urning in Germany in connection his hand in order to ascertain whether with divining rods.

he was possessed with the peculiar disOwing to the criticism and discussion position necessary for performing the aroused by this article, the following fur- divining rod phenomena. After having ther particulars would seem not to be out answered this in the affirmative he at of place:

first demonstrated the working of an iron It may be said that most of the un- rod kept with a certain tension in his favorable criticism made on the above hands whenever this was carried along problem is based merely on the assertion above a silver or gold coin placed on the that the alleged working of the divining table. rod not being accounted for on known As soon as the rod passed the spot in physical laws, the whole matter should question a violent deflection (which acnot be considered worth a scientific dis- cording to the personal disposition is dicussion. How unscientific this method is rected either upwards or downwards) need hardly be pointed out. In fact, so was observed. Herr von Bülow next many novel phenomena which could not began walking along the corridor with have been explained by the laws of nature his rod in his hands when a lively deflecwith which the physicist of say twenty tion was observed at certain places. The years ago was acquainted, have been writer repeated these experiments, and made known in the course of the last few was able likewise to find such a deflecyears that the imprudence of a priori re- tion at about the same points as the exjecting any enigmatical phenomenon is perimenter, and which correspond to the self evident.

beginning and end respectively of an Certain scientists, on the other hand, underground water vein. having tried the divining rid, and hav- Herr von Bülow even calculated the ing been unable to confir its alleged depth of the latter. He also told the working, considered their failure as proof writer his experience as to a supposed against these phenomena.

influence exerted by underground Now as expressly stated in the writer's springs on the sleep of man. He firmly article, these phenomena are distinctly believes (and has confirmed in the case subjective, that is, depending on a cer- of many persons) that whenever a bed is tain personal disposition which is not placed on the top of an underground possessed by everybody.

spring and in the direction of the latter, The writer recently communicated with the sleep of any somewhat susceptible Herr von Bülow-Bothkamp, whose ex- individual is bound to be a troubled one. periments with divining rods have been It should also be remembered that the described in the article referred to, and German Emperor has sent Herr von requested him to demonstrate before him Uslar to the German South West African the phenomena in question.

Colonies, and that according to recent The scientist willingly acquiesced to newspaper report this experimenter has this demand and during the next session been surprisingly successful in finding of the Prussian Lower House of Parlia- out hundreds of underground springs. The importance of such work for coloni- the ground where good conductors of zation purposes need hardly be pointed electricity are found in large amounts in out.

the neighborhood of the surface of the It will be interesting in this connection earth, that is to say, above ore deposits, to refer to an observation made as far most ores being very good conductors of back as in 1747 by a German experi- the electric current. Brown coal, minmenter, that a luminous emanation of eral coal, especially when containing variable shape will appear in the dark pyrites, as well as anthracite, are fairly at points on the surface of the earth good conductors. The difference in the below which there are extensive ore de- intensity of radiation as compared with posits.

points free from ore would seem to be Immediately before or during a thun- recognized by means of photography, derstorm these phenomena are said to thus affording to geologists a rather become specially striking. Similar ob- simple means of locating ore and even servations have been made more recently coal deposits liable to be worked. in North America in the neighborhood The mining work in a pit would also be of ore deposits. Though much should facilitated to a high extent by a similar be ascribed to superstition and to errors process, as in the case of a sudden disof observation, the fact nevertheless has continuance of ore-carrying veins, the been confirmed by recent investigation. nearest deposits would be found out withThe electric emanation given off from out any difficulty. the surface of the earth has in fact been Attempts to utilize this method for repeatedly ascertained by means of pho- practical purposes are being made by tography. Mr. K. Zenger used in this Professor H. Barvir and Mr. Zenger of connection photographic plates impreg- Prague. The invention of an objective nated with fuorescent substances. It method of water finding by Mr. Adolf may thus be taken for granted that the Schmidt of Berne, Switzerland, finally emanations in question occur with a spe- was also mentioned in the writer's precially high intensity at those points of vious article.

An Up-to-Date Substation

By R. F. Perry

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A N example of the electric Edison Company's central station in

substation that is rapidly South Boston, a distance of about ten superseding the old inde- miles. The line through Boston and part pendent power houses is of Newton is underground, but in the that of the Newton and intervening district is run on two cross

Watertown Gas Light arms on top of street railway poles on 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

NEWTON AND WATERTOWN GAS Light Co. ELECTRIC three-phase, 6,900-volt circuits from the

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SUBSTATION.

Commonwealth Avenue Boulevard. The overhead line is of bare stranded aluminum cable equivalent to No. O copper. There is a second tie-line through Dedham and Needhain 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. air SWITCHBOARD IN THE Model SUBSTATION OF THE NEWTON & WATERTOWN Co. cooled transformers relieve them until toward morning when The feeder switchboard with its oil the load has dropped again. These trans- switches, recording and indicating meformers stand on a cement platform over ters, time limit relays and other safety a pit (there is no basement to the build- devices, is on one side of the bank of ing) and a thirty-six-inch blower direct transformers and the distribution board connected to a small motor furnishes the on the other. air draft. The one 500 K. W. unit is a Every means for safely manipulatrecent addition to the original station ing, controlling and recording both equipment, necessitated by the unfore- the 6,900 volt current and the 2,300 seen increase of commercial load. Four volt is installed. All connections are sixty-light tub transformers with their through ducts under the floor and switchboards for the arc lights occupy switchboard fittings are carefully proone side of the building.

tected.

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