Common Science

by Carleton Washburne

The "cigar-box telegraph" shown on page [381] is made as follows: An iron machine bolt (A) is wound with about three layers of No. 24 insulated copper magnet wire, the two ends of the wire (B, B) projecting. The threaded end of the bolt (C) is not wound. A nut (D) is screwed on the bolt as far down as the wire wrapping. The threaded end is then pushed up through the hole in the top of the cigar box as that stands on its edge. Another nut (E) is then screwed on to the bolt, holding it in position. The bolt can now be raised or lowered and tightened firmly in position by adjusting the two nuts (D and E), one above and one below the wood.

A screw eye (F), large enough to form a rest for the head of another machine bolt (G), is screwed into the back of the box about three fourths of an inch below the head of the suspended bolt (A). Two or three inches away, at a slightly higher level, another screw eye (H) is screwed into the back of the cigar box. This screw eye must have an opening large enough to permit an iron machine bolt (G) to pass through it easily. A nut (I) is screwed down on the threaded end of a machine bolt until about an inch of the bolt projects beyond the nut. This projecting part of the bolt is then passed through the screw eye (H) and another nut (J) screwed on to it to hold it in place. This nut must not be so tight as to prevent the free play of the bolt as its head rises and falls under the influence of the vertical bolt. The head of the horizontal bolt rests upon the screw eye which is immediately below the head of the suspended bolt. You therefore have the wrapped bolt hanging vertically from the top of the box, with its head just over the head of the horizontal bolt. There should be about one quarter inch of space between the heads of the two bolts. An electric current passing through the wires of the vertical bolt will therefore lift the head of the horizontal bolt, which will drop back on to the screw eye when the circuit is broken.

Fig. 191. The cigar-box telegraph.

INDEX

An asterisk (*) indicates use of one or more illustrations in connection with reference to which appended.

[A]	[B]	[C]	[D]	[E]	[F]	[G]	[H]	[I]	[K]	[L]	[M]
[N]	[O]	[P]	[Q]	[R]	[S]	[T]	[U]	[V]	[W]	[Y]	[Z]

• Acetylene, carbon and hydrogen in, [315].
• Acids, [351] ff.;
  • action of, on metals, [351]-353*;
  • action of, on cloth, [354]*;
  • action of, on nerves of taste, [354]-355;
  • distinguished from bases by litmus test, [358]-359;
  • neutralization of, by bases, [360]-364.
• Action and reaction, law of, [77]-81*.
• Adhesion, [39], [41]-44;
  • cohesion, capillary attraction, and, [47].
• Air, cooling of, on expanding, [95]-96;
  • liquid, [97];
  • heat carried by, by convection, [118]-119;
  • absorption of light by, [169];
  • sound produced by vibrations of, [174]-181*;
  • pitch due to rapidity of vibrations of, [186];
  • water vapor in, [275]-280*;
  • a mixture and not a compound, [309];
  • part taken by, in making automobile go, [344];
  • limewater test for carbon dioxid in, [375].
• Air pressure, [10] ff., [14]*;
  • height water is forced up by, in vacuum, [19];
  • high and low, [20], [282];
  • winds caused by, [20]-21.
• Air pump, [14]*, [15].
• Alcohol, boiling of, [112];
  • distilling, [113]*-114.
• Alkali, [356];
  • in soap, [357]-358.
• Alloys, definition of, [310].
• Alternating current, defined, [211]-212.
• Alum crystals, experiment with, [265]-266*.
• Aluminum, an element, [299].
• Alum in water, testing with litmus paper, [359].
• Amber, electricity produced by rubbing with silk, [196].
• Ammonia, example of a common base, [356];
  • action of, in cleaning cloth, [358];
  • litmus test of, [359];
  • neutralization of acid by, [363].
• Ampere, defined, [246].
• Analysis, chemical, [370]-376.
• Aneroid barometer, [285]*.
• Arc, the electric, [233]-240*.
• Atoms, description of, [196];
  • electrons and, [197];
  • everything in the world made of, [310]-311;
  • in molecules, [311].
• Aurora Borealis, cause of, [193].
• Automobile, reason for cranking, [210];
  • how made to go, [344]-345.
• Automobile races, overcoming of centrifugal force in, [75]*.
• Automobile tires, reason for wearing of, [80];
  • blow-outs of, [348].

• Baking powder, chemical change by solution shown by, [349]-350;
  • elements of which made, [367]-368.
• Baking soda, a common base, [356];
  • testing with litmus paper, [359];
  • neutralization of sour milk by, in cooking, [362];
  • carbon dioxid in, [366]-367.
• Ball bearings, used to diminish friction, [54]-55.
• Balloon, expansion of, [17]-18, [109]*;
  • reason for rising of, [26];
  • filling of, with hydrogen, [301]-304*.
• Barometer, use of, [280]-285*.
• Bases, substances called, [355]-358;
  • litmus test for distinguishing from acids, [358]-359;
  • neutralization of, by acids, [360]-364.
• Batteries, electric, [203]-205*;
  • different kinds of, [205]*-207*;
  • general principle of all, [206].
• Bell, electric battery for ringing, [204]-205*;
  • working of electric, [255]*.
• Bending of light (refraction), [136]-141*.
• Black, the absence of light, [164].
• Bleaching, process of, [326]-327.
• Blow-out of tire, a real explosion, [348].
• Blue-flame heaters, [319].
• Blueness of sky, reason for, [169].
• Blueprints, making of, [330]-331.
• Boiling and condensing, [107]-115*.
• Borax bead test, [371]*-372*.
• Brass, an alloy, [310].
• Bread making, chemical action in, [365].
• Breath, cause of visibility of, on cold days, [288], [289]*.
• Bronze, an alloy, [310].
• Burning, explanation of, [308], [312]-313.