Chapter XXVI: Part 26

In the foreground is the so-called wet end showing the vats in which the liquid pulp, about 98 per cent water, is pumped. It is screened and then flows on to an endless wire web beyond, where the free water is taken out by drainage and by suction boxes.]

PAPER STOCK.

A large amount of stock of paper mills. This paper is seasoned by holding it in stock and will be later given such surface as is called for.]

Where the paper passes through a bath of coating mixture to a long drying gallery at the end of which it is rewound preparatory to being given the highly finished surface on the calendaring machine.]

The finished rolls of stock pass through rotary cutters which produce the sheets of various required sizes. The paper in the Book of Wonders was cut in sheets 41x55 inches, thus making it possible to print 32 pages on each side of each sheet.]

Illustrations showing manufacture of paper by courtesy of S. D.
Warren & Co.

This picture shows the wonderful Linotype machine by which the type of this book was “set,” as the printers say. The men who operate the machine are compositors. Originally the type matter of books was set by hand and the compositor composed in type what the author of the book had written. By pressing down on the keys which you see in the picture, the compositor sets the words in lines of metal. This machine is almost human. By touching the proper keys, the operator assembles a line of matrices the details of which are explained in another picture, and after this is done the machine automatically casts a slug from them, turns and delivers a slug into a galley ready for use and finally distributes the matrices back into their respective channels in the magazine, where they are ready to be called down again, by the touch of the key button. The latest model linotype has four magazines and can be equipped with matrices which when assembled will cast lines in from six to twelve different sizes and styles of type.

The assembling mechanism is the only part of the linotype where the human mind is applied to the working of the machine. It is necessary for the eye to read what is to be printed, and the mind, through the medium of the fingers, to translate this into assembled lines of matrices; after that the machine acts automatically.]

The keyboard is made up of 90 keys, which act directly on the matrices in their channels in the magazine. The slightest touch on the keybuttons releases the matrix, which drops to the assembler belt and is carried swiftly to the assembler. When a word is assembled, the spaceband key is touched and a spaceband drops into the assembler. When the necessary matrices and spacebands to fill the line have been assembled, the operator raises the assembler by pressing a lever on the side of the keyboard. When the assembler reaches its highest point it automatically starts the machine and the matrices are transferred to the casting position.

This illustration shows the manner in which matrices are constantly circulated in the Linotype. From the magazine they are carried to the assembler, then passed to the mold, where the line is cast, and from the mold after casting they are raised to the top of the machine and redistributed to their proper channels in the magazine.

The Linotype is sometimes called a typesetting machine, but this is not correct: it does not set type. It is a substitute for typesetting. It is strictly speaking a composing machine, as it does composition but its product is not set type, but solid slugs in the form of lines of type with the printing face cast on the edge.

It is in reality four machines so arranged that they work together in harmony--the magazine, the assembling mechanism, the casting mechanism and the distributing mechanism. The magazine is at the top of the machine sloping to the front at an angle of about 31 degrees, and consists of two brass plates placed together with a space of about five-eighths of an inch between. The two inner surfaces are cut with 92 grooves or channels running the up and down way of the magazine, for carrying the matrices. The matrices slide down these channels on edge, with the face or punched edge down, and the V-end extending toward the upper part of the magazine. Each of these channels will hold twenty matrices.]

ONE-LETTER AND TWO-LETTER MATRICES.

Linotype matrices are made of brass. In the edge of each matrix is either one or two letters or characters in intaglio. The thickness of the individual matrices is dependent on the width of the character. By an ingenious arrangement either one-letter or two-letter matrices can be used in the same machine, and either character on a two-letter matrix can be used at will.

The two-letter matrix bears two characters, one above the other, one of which may be a Roman face and the other an italic, small capital, or black face. If a line is to be composed partly of the Roman face, which is in the upper position on the matrix, and partly of the other face, which is in the lower position, this is accomplished by means of a slide on the assembler operated by a small lever.

When the lower characters on the matrices are required, the slide is shifted and the matrices are arrested at a higher level, so that the lower characters align with the upper characters of the other matrices in the assembler. When the slide is withdrawn the matrices are assembled at the lower level. By means of this simple contrivance, a line may be composed partly of one face, partly of the other face, or entirely of either face.]

Linotypes are guaranteed to be capable of setting above 5000 ems of 6 point per hour, and this output is widely obtained in commercial printing offices with first class operators. When a compositor speaks of the amount of type he sets per hour or day he speaks of “ems.” A column of type matter is so many “ems” wide. The term “em” means the square of the particular size of type that is being set. Thus if a column is said to be 13 ems wide it means that an em quad or square, could be set 13 times in the width of the column. Type is graded according to size by points. Machine type for book work runs from 5 points to 12 points. A point is one seventy-second of an inch, that is, there are 72 points to an inch. This guarantee, however, by no means indicates the limit of speed at which the machine can be operated, as evidenced by records of 10,000 to 11,000 ems per hour maintained for an entire day. The rapidity of the Linotype is limited only by the ability of the operator to manipulate the keys, and the extreme capacity of the machine has never yet been attained.]

SECTIONAL VIEW OF MAGAZINE SHOWING CHANNEL FULL OF MATRICES.

This picture shows the machine with part of the magazine top and side removed. We can thus see how the matrices are arranged in their respective grooves in the magazine. When one of the keys of the keyboard is pressed down the first matrix in the corresponding grove in the magazine escapes and drops upon a conveyor belt and is carried in its proper order to an assembler, which answers much the same purpose as a printer’s stick. The correct spacing or justification of the line of matrices is accomplished by means of spacebands, which are assembled automatically between the words in the line by the touch of a lever at the left of the keyboard.]

Instead of producing single type characters, the Linotype machine casts metal bars, or slugs, of any length desired up to 36 ems, each complete in one piece and having on the upper edge, properly justified, the characters to print a line. These slugs are automatically assembled in proper order as they are delivered from the machine, when they are immediately available either for printing from direct or for making electrotype or stereotype plates. They answer the same purpose and are used in the same manner as composed type matter.]

LINE OF MATRICES BEING LIFTED TO DISTRIBUTOR

After the slug has been cast, the matrices are carried up to the second transfer position, where they are pushed to the right, and the teeth in the V at the top of the matrices engage the grooves in the distributor bar of the second elevator, which descends from the distributor box at the same time that the matrices rise to the second transfer position. The second elevator then rises toward the distributor box, taking the matrices with it, but leaving the spacebands; these are then pushed to the right and slide into the spaceband box, to be used again.

As the second elevator rises toward the distributor box with its load of matrices, the distributor shifter lever moves to the left until the elevator head has reached its place by the distributor box. It then moves back to the right and pushes the matrices off the second elevator distributor bar into the distributor box, where they meet the “matrix lift” and are lifted, one at a time, to the distributor screws and distributor bar proper. The teeth in the matrix and the grooves in the bar are so arranged that when a matrix arrives at a point directly over the channel in which it belongs, it “lets go” and drops into its channel.

If, however, there is a matrix in the line which was not designed to drop into one of the channels operated from the keyboard, it will be carried clear across the distributor bar and dropped into the last channel, and from there it will find its way to the sorts box.]

The casting mechanism consists of the metal pot, mold disk, mold, ejector, and trimming knives. The illustration shows a cross-section of the metal pot, mold disk, and mold, with a line of matrices in the casting position. When the line of matrices leaves the assembler, they pass to a position in front of the mold disk. The disk makes a one-quarter turn to the left, which brings the mold from the ejecting position, where it stands while the machine is at rest, to the casting position. It then advances until the face of the mold comes in contact with the matrices. The metal pot advances until the pot mouthpiece comes in contact with the back of the mold; at this point the pump plunger descends and forces the metal into the mold and against the matrices. The pot then recedes, the mold disk withdraws from the matrices and makes three-fourths of a revolution to the left, stopping in the ejecting position, from which it started. The slug is ejected and assembled in the galley.

During the last revolution of the disk the bottom of the slug is trimmed off, and in the process of ejection the sides of the slug are trimmed, so that when it drops in the galley the slug is a perfect line of type, ready for the form.]

As the slugs of type, each of which represents a line, come from the linotype machine, they are arranged in order in a brass holder the width of the line of type, called a “galley.” This holder is about twenty inches long. As soon as it is filled one of the men in the typesetting office takes it to a proof press where he makes a rough impression of it. He runs an ink covered roller over the top of the slugs, lays a piece of blank paper on it and then either runs another roller over it or puts it in a hand press and secures an impression of the type just as it is. This is called making a “galley proof.”

The galley proof is then sent to the proof-reader who reads it carefully and indicates such errors in setting as appear and must be changed. Before correcting the actual type, however, the composing room sends the galley proof to the one who is publishing the book. The publisher also reads the proof over carefully and, if he does not wish to change any of the wording, he sends it back to the composing room with his “O. K.” attached in writing. If he wishes to change the wording, he does so and the galley proof is then returned to the composing room marked “O. K. after corrections and changes are made.”

The linotype operator then makes whatever changes are desired or necessary by setting new lines where mistakes or changes occur. If there is only one wrong letter in a line, he must reset the whole line as the machine, as you remember, only turns out solid lines of type. A revised proof is then sent to the publishing office and, if no further changes are to be made, he gives instructions to have the “galley” made up into pages. How the pages are made up is shown in the next picture.]

When the revised proofs come back from the publisher ready to be made into pages, the publisher has marked on same what pictures are to go on the pages of the “make up” as this is called. The compositor then picks out the pictures in the form of cuts which are to go on the different pages and puts them in the page first. He then arranges the type matter from the galley proof around, above or below the pictures, puts in the proper headings and takes a “final proof” of how the pages are arranged to look. If this is satisfactory the publisher puts a “final O. K.” on the proof in writing and the page is ready to be printed. Thus the book is made up page by page. No page is printed without the O. K. of the publisher and so, if there are any errors still in the page, the publisher is responsible.]

PRINTING THE BOOK OF WONDERS

This picture shows the pages of the Book of Wonders being printed. Thirty-two pages are printed on each side of a sheet of paper at one time. A printing office is a busy place as can be seen from the picture. As soon as the ink is dry on the printed sheets they are taken to the bindery where they are folded and sewed ready to have the covers put on.]

When the printed sheets are received in the bindery they are fed into a folding machine which is shown here. A sheet of 64 pages is folded and cut and delivered in four sections of 16 pages each ready to be gathered.]

Courtesy of the J. F. Tapley Co. New York.

Here we see the girls at work operating the sewing machines which sew the sections together at the back side of the book.]

Courtesy of the J. F. Tapley Co., New York.

In this picture we see the “case makers” at work making the covers on which the actual book is bound.]

Courtesy of the J. F. Tapley Co., New York.

How Is Photo Engraving Done?

~HOW THE PICTURES IN THIS BOOK ARE MADE~

The first step is the making of the halftone negative which differs from an ordinary negative in being made up of different sized dots instead of shades of gray. This result is obtained by photographing the picture through a halftone screen consisting of two pieces of glass, ruled with black lines and cemented together so the lines cross at right angles and leave small squares of clear glass.

The effect of making the negative in this way is to represent the different shades from black to white by large or small dots. Wet plate photography is usually used in this process because the film is thinner and more intensely black besides being cheaper than dry plates.

New Process Engraving Co.

This cut shows a portion of a halftone cut enlarged so that the dots can be seen very plainly.]

Having made the negative the next step is to make a printing plate from it. To do this, a piece of metal, copper if the work is fine, and zinc for coarser work, is coated with a solution which is sensative to light, fish glue is commonly used to which is added a small amount of ammonium bichromate. The metal being coated and dried, it is put in a very strong frame with the negative and squeezed together so that they are in perfect contact. A powerful light is now directed upon the negative with the metal behind it, the result being that wherever the light goes through the white spaces in the negative, the coating on the metal is rendered insoluble. Where the dots on the negative are, the light is unable to get at the coating so that when the metal is removed from the frame and thoroughly washed this part of the coating washes away, leaving the part which the light got at attached to the metal. This is now heated until the enamel, as the coating is called, turns dark brown and the picture can be easily seen.

The picture is now on the metal but it must be made to stand out in relief before it can be used for printing from, so it is put in a bath of acid which eats away that part of the metal left uncovered by the washing away of the coating and this leaves the dots which make up the picture standing up in relief. A roller covered with very thick paste-like ink is now rolled over the picture, or cut as it is now called, and when a piece of paper is pressed against the ink covered cut each little dot leaves a mark of ink on the paper the total making up the picture as we see it.

There are many more wonderful things connected with the making of cuts such as the routing machine which has a tool that revolves so fast that it turns around 300 times while the clock ticks once, and other machines which cut hard metal as easily as you can cut a potato with a knife.

Colored pictures are also made by the process outlined above. The picture is photographed three times with a different colored piece of glass in front of the lens, the result being three negatives, one of which has all the blue, one all the red and the other all the yellow in the picture. By making cuts from each negative and printing them on top of one another in yellow, red, and blue, the original picture is reproduced in all its colors. This is how all our pretty magazine covers are made.

ACKNOWLEDGMENT

The Editors of the Book of Wonders make acknowledgment herewith to the following. All mentioned have been a great assistance in making the book not only possible but authentic:

Spencerian Pen Co.
Eastman Kodak Co.
American Telephone & Telegraph Co.
Remington Arms Co.
Bethlehem Steel Co.
American Portland Cement Manufacturers Assn.
Brainerd & Armstrong Silk Co.
Corticelli Silk Co.
Curtiss Aeroplane Co.
U. S. Beet Sugar Industry.
Hartford Carpet Co.
Haynes Automobile Co.
Jacobs & Davis, Engineers.
Pennsylvania Railroad Co.
Endicott, Johnson & Co.
United Shoe Machinery Co.
Sherwin-Williams Co.
Pittsburgh Plate Glass Co.
The Colliery Engineer.
Lake Torpedo Boat Co.
Western Union Telegraph Co.
New York Edison Co.
Westinghouse Lamp Co.
Consolidated Gas, Electric Light and Power Co. of Baltimore.
Browning Engineering Co.
The White Star Line.
Marconi Wireless Co.
Plymouth Cordage Co.
American Woolen Co.
The Vitagraph Co.
The B. F. Goodrich Co.
The Goodyear Rubber and Tire Co.
The Lexington Chocolate Co.
The Hecker-Jones Milling Co.
The White Oak Mills.
The H. C. White Company.
A. I. Root Company.
Kohler & Campbell.
Browne & Howell Co.
P. & F. Corbin.
Otis Elevator Co.
Scientific American.
Joseph Dixon Crucible Co.
Homer W. Laughlin Co.
S. D. Warren & Co.
C. B. Cottrell & Sons Co.
Mergenthaler Linotype Co.
J. F. Tapley & Co.
New Process Engraving Co.
Mutual Film Corporation.
Tobacco Trade Journal Co.
McClure’s Magazine.
James Arthur.
Seth Thomas.
American Locomotive Co.
New York Central Railroad Co.
Columbia Rope Co.
Carl Werner.
National Wool Growers Assn.

INDEX

=Acid=, carbonic, what it is, 509

=Aerial=, on ship, (illus.), 455

=Aeroplanes=, English Channel crossing (illus.), 132
Curtiss biplane (illus.), 131
first demonstrations of, 130
first flight in Europe, 129
first man-carrying (illus.), 128
first successful (illus.), 126
gas motors used in, 130
gliding, 137
greatest present value of, 136
records of, 131
red wing (illus.), 131
what two brothers accomplished for, 130
Wright Bros.’ inventions, 130

=Age=, why do we, 196

=Air=, does it move with the earth? 400
does it weigh anything? 398
dust in, 38
extend, how far does, 243

=Airlocks=, description of in tunnel building, 213

=Ammunition=, first invention of, 40
fixed, 47
in prehistoric times, 40

=Animals=, can they think? 194
is man an, 180
that leap greatest distance, 122
which foretell weather, 240

=Anthracite seams= (illus.), 260

=Aqueduct= (illus.), 505

=Are= matches poisonous, 294

=Armor=, in the Middle Ages, 44

=Army=, wireless in the, 448-451

=Are= there two sides to the rainbow? 254

=Arrow=, what causes it to fly? 408

=At= what point does water boil? 220

=At= what rate does thought travel? 242

=Australian Ballot=, where first used, 122

=Automobile= (illus.), axle, location of, 186
beginning of, 183
carburetor, location of, 184
carburetor, use of, 184
chassis, complete, 188
cog-wheels, use of, 183
cog-wheels, location of (illus.), 183
crankcase, location of (illus.), 183
cylinder, location of (illus.), 184
drive shaft, location of (illus.), 187
electric generator, use of, 185
exhaust, 184
fenders, location of, 188
fenders, use of, 188
finished car (illus.), 189
first American (illus.), 189
fly-wheel, location of (illus.), 183
fly-wheel, use of, 183
frame (illus.), 186
gasoline, what it does, 183
gasoline tank, location of, 187
gears, location of (illus.), 183
gears, use of, 183
heart of (illus.), 184
how improved, 190
magneto, location of, 185
magneto, use of, 185
marvellous growth of twenty years, 189
modern power plant complete, 190
oil pan, use of, 184
oil pump, location of, 184
piston, location of (illus.), 183
piston, use of, 183
power plant, an (illus.), 185
radiator, location of (illus.), 188
radiator, use of, 188
ready for the wheels, 187
second stage of construction (illus.), 186
self-starter, location of, 185
self starter, use of, 185
Smithsonian exhibit of complete power plant, 190
springs, location of (illus.), 186
springs, use of, 186
steering gear, location of (illus.), 187
street scene 20 years ago, 189
transmission, location of, 186
tire pump, use of, 185
tires, how made, 382
transmission, use of, 186
water pump, location of, 185
water pump, use of, 185
what the completed chassis looks like (illus.), 188

=Bacon, Roger=, discoverer of gunpowder, 44

=Balance=, effect of sunlight on, 37

=Baldness=, chief course of, 143
why some people are, 143

=Ball=, why it bounces, 63
bearings, what they are, 180

=Balloon=, what keeps it up, 199
why it goes up, 199

=Ballot=, when first used, 122
Australian, where first used, 122

=Bearings, Ball=, what they are, 180

=Bee=, how it lives, 336
why it has a sting, 336

=Bell, Alexander Graham= (illus.), 70
first telephone, 72

=Bend=, why things, 62

=Biplanes=, Curtiss (illus.), 131
in flight, Curtiss (illus.), 136

=Birds=, how do they find the old home? 408
how they learn to fly, 178
how they find their way, 407
reproduction of life in, 179
why do they sing? 408

=Birds’ Eggs=, why different colors, 233

=Blasting= gelatin, definition of, 206

=Bleriot, M.=, first European flights, 129

=Blotter=, capillary attraction of, 18
how it takes up ink, 18

=Blush=, why do we, 194

=Boat=, how it can sail under water, 269
hydroplane of submarine, 270
inside of a submarine (illus.), 272

=Bodies=, swiftest moving, 25

=Boiling= point of water, 220
what makes water, 220

=Boring mill= (illus.), 56

=Bottles=, gurgle in, 63

=Bounce=, why a ball will, 63

=Bow=, long (illus.), 42

=Bow-and-Arrow=, invention of, 43

=Boxes=, match, how made, 294

=Brazil, Emperor of=, receives first words over telephone, 74

=Bread=, how flour is made, 462
difference in Graham and whole wheat, 461
grinding wheat (illus.), 464
harvesting wheat, 460
loaves of world (illus.), 459
origin and meaning of, 460
purifying machine (illus.), 463
separating fibre germs (illus.), 463
wheat conditioning (illus.), 462
when wheat was first used in making, 461
where it comes from, 460
why so important, 460

=Break=, why things, 62

=Breech=, of a big gun, 53

=Breech-loaders= in Civil War, 48
in rifle, 47

=Brush=, in writing, invention of, 13
in writing (illus.), 13

=Bullets=, cupro-nickel used in, 50
grading of, 51
weighing of (illus.), 49

=Buildings=, concrete, how made (illus.), 100

=Buttons=, on sleeves, 64

=Building=, tallest in the world (illus.), 395-508
what holds it up? 496

=Building foundations=, construction of, 496
compressed air, use of (illus.), 500
cutting piles with a hot flame (illus.), 498
driving steel piles, 496
piles filled with concrete (illus.), 499
piles, length of, 497
piles, sinking of (illus.), 497
use of oxyacetylene, 498

=Cable, laying= armoring machine (illus.), 437
arrived on other side, 433
bulge (illus.), 437
gear-paying-out (illus.), 431
Great Eastern, the, 434, 437
landing of (illus.), 433
machinery on cable ship (illus.), 431
paying-out machine (illus.), 431
shore end of (illus.), 429
storing of, aboard ship (illus.), 430
what they look like when cut in two (illus.), 428

=Cable, ocean=, Continental Morse Code, 438
how dropped (illus.), 432
how repaired (illus.), 435
inventor of, 434
laid, how, 429
man who made it possible, 434
pioneers of, 434
signals as received (illus.), 438
what is it made of, 429

=Cable, repairing=, grapnels (illus.), 435
how repaired, 435
on rocky shore, (illus.), 438
powerful engines used (illus.), 436
splicing of (illus.), 436

=Cable, service=, map of Trans-Atlantic, 439

=Cable, vault=, of telephone (illus.), 67

=Cabriolet=, 122

=Cacao, beans=, bags of (illus.), 388
how cured, 392
nibs, 392

=Cacao=, flaked, how made, 392
how gathered, 391
pods, how gathered, 391
free, discovery of, 388
and chocolate, difference between, 389

=Cackling=, why a hen, 233

=Calibre= of a gun, 53

=Calico=, name, where from, 123

=Camera=, 22
first moving picture, 375

=Can= a bee sting? 536

=Can= animals think? 194

=Candles=, did they come before lamps? 294
why it burns, 21
why it gives light, 21
why you can blow out, 21-36
when introduced, 296

=Candy=, why do children like? 409
why does eating candy make some people fat? 409

=Carbon=, 352

=Carbonate of Soda=, used in developing, 23

=Carburetor=, in gas engine, 184

=Carpets=, carding machine (illus.), 170
dyeing the yarn, (illus.), 170
examining and repairing (illus.), 173
how yarn is dyed, 170
manufacture of (illus.), 169
modern, how made, 169
packing for shipment (illus.), 173
processes, 169-170-171, 173
stamping designs, 173
view of factory (illus.), 172
weaving, by machine (illus.), 171
wool, packing machine (illus.), 169
wool sorting, 170

=Cartridges=, invention of, 48
types of (illus.), 49

=Cave=, man who invented ammunition, 40

=Cement=, alumina in, 95
amount used in United States, 95
arch, 95
bagging (illus.), 99
bridges, 95
bucket (illus.), 97
burned (illus.), 98
calcined (illus.), 98
clay in, 95
crusher (illus.), 97
dams, 95
fireproof, 95
grinders (illus.), 98
industry, 95
in water, 95
kiln (illus.), 98
lime in, 95
machine (illus.), 97
marl in, 95
mill (illus.), 96-98
mixing (illus.), 99
mortar, 99
on farms, 95
origin, 95
plastic, 95
Portland, 95
powder (illus.), 98
quarry (illus.), 96
reinforced, 95
rock (illus.), 95-97
sewers, 95
shale in, 95
shovel (illus.), 96
sidewalks, 95
silica in, 95
strength of, 95
subways, 95
tunnels, 95
walls, 95
what is it, 95
what made of, 95
what used for, 95
weighing (illus.), 99
where obtained (illus.), 97

=Chalk=, where it comes from, 18

=Chattering=, why do my teeth, 218

=China-making=, blungers, 404
clay, in making dishes, 405
decorating cups (illus.), 404-406
dishes, how shaped, 405
glazing plates (illus.), 404
grinders (illus.), 404
how the dishes are shaped, 405
molding (illus.), 405
pressing water from clay (illus.), 405
pulverizing materials, 404
pulverizing mill (illus.), 404
saggers (illus.), 406
taking the dishes from kiln (illus.), 406

=Chinese=, probable discovers of gun powder, 44

=Chocolate=, broma, what it is, 390
cacao beans (illus.), 388
cacao pods, (illus.), 391
cacao tree, discovery of, 388
cocoa butter, 390
cocoa mill (illus.), 390
cocoa roaster (illus.), 390
cocoa shells, 390
cracking mill, 389
cream mixing (illus.), 393
difference between and cacao, 394
dipping department, 394
finisher (illus.), 392
flaked cocoa, 392
heating machine (illus.), 393
how are chocolate candies made? 394
how made, 392
making, 393
milk, how made, 394
mill (illus.), 392
mixer (illus.), 393
shell separator (illus.), 389
what cocoa butter is, 390
wrapping individual, 394

=Cigars=, how they are made, 517

=Clay=, what is, 495

=Circles=, tendency to walk in, 91

=Clinking= glasses, how it originated? 232

=Clock=, age of, 319
largest in the world (illus.), 321
machinery which runs a big (illus.), 322
in Independence Hall (illus.), 323
in New York City Hall, 323

=Cloth=, beaming (illus.), 89
Burling (illus.), 88
Burr picker, 87
chloride of aluminum in making, 98
English cap spinning (illus.), 89
finished, ready for market (illus.), 90
finish perching (illus.), 90
fulling (illus.), 90
how made from wool, 85
how made perfect, 83
how woolen is dyed, 87
mending perching (illus.), 88
napping, 89
piece dyeing (illus.), 90
ring twisting (illus.), 89
sulphuric acid solution in making, 87
teasel, 89
weaving and scouring (illus.), 88
web, 86
woolen mule spinning (illus.), 89
worsted carding (illus.), 85
yarn inspecting (illus.), 89

=Clothes=, cost of wool in a suit of, 83
of wool, 80
wool in one suit of, 83

=Coal=, anthracite, 257, 258
anthracite seams (illus.), 260
breaker (illus.), 257
cars ready to go to surface (illus.), 260
dangers to the miners, 262
electric cap lamp (illus.), 264
firedamp, 262
gas illuminating from, 299
gases, 262
history of the safety lamp (illus.), 263
how the miners loosen the coal (illus.), 261
how the slate pickers work (illus.), 259
lamp which saves many lives, 263
man who invented the safety lamp, 264
mine workers that never see day light, 258
mules and their drivers (illus.), 258
peat, 262
safety lamp and firedamp, 262
seams (illus.), 260
shaft gate (illus.), 260
slate pickers (illus.), 259
soft, 259
spiral slate pickers (illus.), 259
stable underground (illus.), 258
undercutting with compressed air machines (illus.), 261
undercutting with pick (illus.), 261

=Cocoa=, see Cacao

=Cocoon=, description of, 115
completed (illus.), 116
from which moths have emerged (illus.), 117
how silk is reeled from, 118
moths emerging from (illus.), 117
number required to one pound of silk, 117
silkworm beginning of (illus.), 116
silkworm, preparing for making of (illus.), 116

=Coins=, gold, 266
in glass of water, 38
silver, 266

=Cohesion=, definition of, 219, 220

=Cold=, why some things are, 144

=Color=, exposed to light rays, 36
in paint, 229
what it is, 123

=Colors=, different in birds’ eggs, 233
in sunset, cause of, 253

=Color=, of rainbow, 253
red, why it makes a bull angry, 490

=Columbus=, brought first sheep to America, 80

=Comb honey=, development of (illus.), 529

=Compounds=, compared with elements, 349

=Compressed air=, method in building tunnels, 211

=Concrete=, buildings (illus.), 100
construction (illus.), 100
decay, 101
engineering, 102
forms (illus.), 100
houses (illus.), 101
loads (illus.), 100
mold, 101
ornamental (illus.), 100
practical uses of (illus.), 100
rusting, 100
Silo (illus.), 102
stable (illus.), 102
sun dial (illus.), 101
tensile strain, 104
tower (illus.), 102
walls (illus.), 100
water tower (illus.), 102
what it is, 95
wood, 102

=Confucius=, philosophy written with brush, 13

=Cooking=, when first used, 308

=Copper=, as a conductor of electricity, 267
wire, telegraph, 266

=Corn plant=, how pollen fertilizes, 170
why it has silk, 176

=Corn Silk=, what it is for, 176
baling presses (illus.), 476

=Cotton=, drawing frames (illus.), 472
slashers (illus.), 475
spinning frames (illus.), 473
warping machine (illus.), 474
what nation produces the most, 477
how much cloth will a pound of cotton make, 477
mill (illus.), 471
cloth, first steps in making, 472
putting fiber on bobbins (illus.), 473
cloth finished (illus.), 476
who discovered, 477
weave room, 475
where it comes from, 470
lapper machines, 471
card room (illus.), 472
bobbins (illus.), 473
dye-house (illus.), 474
beaming frames (illus.), 475
inspecting tables (illus.), 476
field a southern (illus.), 470
breaker machines (illus.), 471
slubber machines (illus.), 472
speeders (illus.), 473
spooling machine (illus.), 474
shipping (illus.), 476
what used for, 477
cloths, what are the principle, 477

=Counting=, man, himself, 19
in tens, 19
in twelves, 20

=Crying=, what makes us, 195
when hurt, why we, 93

=Cross-bow=, invention of, 44

=Crude rubber=, how treated, 378

=Culverins=, early type of, 45

=Cylinder in gas engine= (illus.), 184

=Darkness=, cats can see in, 91
some animals can see in, 91
why we cannot see in, 91
why we fear, 352

=Deep sea diving=, the telephone adjusting (illus.), 202
coming up (illus.), 204
cost of outfit, 203
helmet, putting on (illus.), 202
just before going down (illus.), 204
outfit, 202
shoes, putting on (illus.), 202
suit, putting on (illus.), 202
telephoning from bottom, 203
telephone, testing the (illus.), 203
testing, final (illus.), 203
water pressure at varying depths, 203
wealth recovered by diving, 204
weight of outfit, 203

=Deer-stalking with the cross-bow= (illus.), 42

=Detonators=, in firearms, 47

=Developer=, Pyro, in photography, 23

=Diamonds=, what made of, 351

=Did= candles come before lamps? 294

=Die=, why do we have to, 245

=Difference= in woolens and worsteds, 84

=Dimples=, what causes, 352

=Discovery= of gunpowder, 44

=Discovery= of stringed musical instruments, 479
telephone, 71

=Diver’s= task made easy (illus.), 284

=Diving, deep-sea=, the telephone adjusting, (illus.), 202
cost of outfit, 203
hats of divers, 204
just before going down (illus.), 204
helmet, putting on (illus.), 202
shoes, putting on (illus.), 202
suit, putting on the (illus.), 202
suit, what consists of, 202
telephone from bottom, 203
telephoning, testing the (illus.), 203
testing final (illus.), 203
water pressure at varying depths, 203
wealth recovered by diving, 204
weight of outfit, 203

=Dixie=, what name means, 124
where name originated, 123

=Does= air weigh anything, 398

=Does= the air surrounding the earth move with it? 400

=Does= thunder sour milk, 196

=Does= light weigh anything? 37

=Does= the sun revolve on its axis? 511

=Do= father and mother plants always live together? 176

=Do= the ends of the rainbow rest on land? 254

=Do= the stars really shoot down? 255

=Dog=, why he turns round before lying down, 229

=Dolls=, why girls like, 368

=Dom Pedro=, Emperor of Brazil, who saved the telephone, 73

=Do= plants breathe? 241

=Draft=, created by chimney, 37

=Dreams=, cause of, 366
nightmare, 367
what makes us? 366

=Drinking=, origin of clinking glasses, 232

=Driving shield=, airlock bulkhead (illus.), 210
erector (illus.), 210
in tunnel building (illus.), 208
inventor of, 209
tunnels, front view (illus.), 209

=Ducks=, why water runs off backs of, 233

=Dust=, in air, 38
what it is, 104

=Dyeing=, silk, 121

=Earache=, what causes, 410

=Earth=, how big it is, 124
light surrounding, 38

=Echo=, what makes an, 200
whispering gallery, 201

=Eggs=, birds why different colors, 233
silkworm, how imported, 111

=Egyptians=, how ancients wrote, 12

=Electric arc=, temperature of, 35

=Electric current=, what it is, 334

=Electricity=, conductors of, 331
current, 334
good conductors, 331
how discovered, 333
non-conductors, 331
what is, 329

=Electric lighting=, arc-light, 307
Edison’s first lamp (illus.), 306
incandescent carbon lamp (illus.), 306
Mazda lamp (illus.), 306
tantalum lamp (illus.), 306
Tungsten metal lamps, 305
when introduced, 305

=Elements=, carbon, 352
compared with compounds, 349
hydrogen, 349
nitrogen, 350
oxygen, 349
what an is, 349

=Elevator=, description of (illus.), 397
installation (illus.), 396
principal parts of, 396
why does not the car fall? 397

=Emperor=, saved the telephone, 73

=Emperor of Brazil=, receives first message over first telephone, 74

=Engine, gas= (illus.), 181-182
carburetor, 184
cylinder (illus.), 184
horse-power, of, 256

=Exchange=, first telephone, 75

=Exhibition=, of first telephone at Centennial, 74

=Experiments=, with mirror resultant in photograph, 22

=Exploding=, a submarine mine, 34

=Explosions=, how they break windows, 62
in gas engines (illus.), 182
of submarine mines (illus.), 34
what happens in, 205

=Explosives=, definition of, 205
blasting gelatin, 206
gun-cotton, 206
nitroglycerine, 206

=Eye=, of a submarine (illus.), 274

=Eyes=, closed, walking with, 91
hand quicker than, 376
help brain in walking, 91
in some pictures follow you, why, 36
keeping body balanced, 91
nature’s way of protecting, 38
protecting with tears, 38
sparkle when merry, why, 92
why we can’t sleep when open, 92
why we see stars when hit on, 268

=Eye-wash=, tears as an, 38

=Fabrics=, worsted, 85

=Fahrenheit=, what is meant by, 221
why so called, 221

=Fastest= camera in the world, 25

=Fathers and Mothers=, do plants have, 175

=Federal Government=, grazing fee paid to, 82

=Fertilization=, in birds, 179
how corn plant fertilizes, 176
of fishes, 177

=Fight=, of Merrimac and Monitor, 32

=Film=, before and after snapshot, 23
sensitive, 23

=Finger prints=, arch, (illus.), 520
composite (illus.), 521
of different people, 521
enlargements of, 524
how they identify us, 520
impressions of orang-outang (illus.), 522
loop (illus.), 520
palmary impressions (illus.), 522
specimen form of, record (illus.), 525
spike that caught a criminal (illus.), 524
thieves caught through their, 523
thumb imprint on bottle (illus.), 523
thumb impression on cash box (illus.), 523
thumb mark on a candle (illus.), 523
where first used, 522
whorl (illus.), 521

=Fingers=, why they hurt when cut, 143
why we have ten, 142

=Finger nails=, why we have, 142

=Fire=, alarms when first used, 308
first apparatus to fight, 308
first fire department, 308
first real, fire engine, 308
gases put out, 37
how man discovered, 289
how man learned to fight, 208
how man learned to make a, 289
mark, of civilization, 290
why it goes out, 37
why is it hot? 401
why put out by water, 222

=Fire making=, drilling (illus.), 289
drilling with bow string (illus.), 290
drilling, two persons (illus.), 290
first matches (illus.), 292
flint and pyrites (illus.), 290
flint, introduction of (illus.), 291
plowing (illus.), 290
pyrites (illus.), 290
rubbing sticks together, 42
sawing (illus.), 289
steel and flint (illus.), 291
tinder box (illus.), 291
tinder box, pistol (illus.), 291
with matches, 292

=Firedamp=, 262
explosion in safety lamp, 262

=Firearms=, first crude efforts of, 45
first real (illus.), 45
fuse of, 45
in early Chinese history, 44
first trigger of, 45

=Firing=, mortar, causes gas-rings, 27

=First= man-carrying aeroplane, 128
real telegraph, 421
stringed musical instrument, 480
telephone (illus.), 72
telephone line, 72
telephone switchboard (illus.), 74

=Fishes=, how they are born, 177
how they come to life, 177
motion in swimming, 233
what the eggs are, 177
why they cannot live in air, 232

=Flag=, made, how was American, 310
made, when was American? 310

=Flash pan=, early type, 45

=Flaxseed oil=, what it is, 227

=Flight=, of projectile, long, 30

=Flint-lock=, invented in seventeenth century, 46
invented by thieves, 46
still in use in Orient, 46

=Floor=, sounds through a, 79

=Flour=, bolters (illus.), 465
how made, 462
purifying machine (illus.), 463
sieves, 465

=Flowers=, why they have smells, 176

=Flying=, how birds learn, 178
boat, wonderful (illus.), 133
first Langley monoplane, 126
first successful aeroplane (illus.), 126
machine, first models, 127
some of the men who helped, 126
ten years of (illus.), 137

=Flying boat=, fun in (illus.), 135
gliding by, 137

=Flying boat=, interior arrangement (illus.), 134
monoplane type (illus.), 135
six-passenger hull (illus.), 134
speed of (illus.), 135
the wonderful, 133
views of (illus.), 133

=Flying machines=, 126
Bleriot flew in Europe (illus.), 129
Curtis biplane in flight (illus.), 136
Dr. Langley’s flying (illus.), 127
early types of, 127
first demonstrations, 130
first flight in Europe with, 129
first man-carrying aeroplane, 128
first models, 127
flying boat, 133
flying boat, exterior arrangement, 134
gliding experiments, 137
government interest in, 138
hull of flying boat, 134
interesting governments in, 138
Wright Bros., first flights, 130

=Focus=, in eye, 22

=Fog=, what it is, 105

=Food=, how we learned to cook, 308

=Foreign monoplanes=, some famous (illus.), 132

=Forsythe, LL.D. J.=, inventor of the primer, 47

=Freckles=, what makes them come, 125

=Fuse=, for firearms in early history, 45

=Funditor=, 42

=Gas=, acetylene, 305
definition, 348
first structure to be lighted by, 302
in coal mines, 262
water, 305

=Gas, illuminating=, Baltimore first city to use, 302
carbon in, 302
discovered, when, 302
first American house to use, 302
first practical demonstration of, 302
generator house (illus.), 299
holder (illus.), 298
how it gets into jet, 302
how it is purified, 303
how made, 303
how the meter works, 304
hydrogen in, 302
impurities removed from (illus.), 301
jet, the story in a, 303
made of, 302
meter, description, 304
purifying boxes (illus.), 301
removing tar from, 300
shaving scrubbers (illus.), 300

=Gasoline engine= (illus.), 181, 182

=Gases=, generated at gun muzzle, 27
how expelled in gun ingot, 55
hydrogen, 349
nitrogen, 350
oxygen, 349
tendency to put out fire, 37

=Gas-rings=, in firing motor, 27

=Gatling=, inventor of guns, 310

=Gelatine=, in photography, 23

=Gestures=, talking by, 18

=Ghosts=, what are they? 367

=Glad=, why do we laugh when, 92

=Glass=, why it cracks, 63
how long known, 247

=Glass, plate=, casting (illus.), 249
commercial, 246
plate and window glass compared (illus.), 252

=Glass, plate, making=, annealing, oven, 249
beveling, 247
blanketing, 252
clay mixing (illus.), 248
clay trampling (illus.), 248
clay used, 247
grinding table, 250
materials used in, 247
mercury, 253
nitrate of silver, 253
pots (illus.), 248
pots, drying of, 248
pots, length of usefulness, 248
silvering, 247
skimming the pot (illus.), 249
treading, 247

=Glow-worm=, why does it glow? 231

=Gold=, why is it called precious? 266

=Gong=, why does it stop when it has been sounded, 78

=Good luck=, why a horseshoe brings? 311

=Graphite= in lead pencils, 468

=Gravitation=, what is, 267

=Gravity=, center of, in gun, 61

=Gravity=, force of, 61

=Greek fire=, in early history, 44

=Growing=, why do we stop, 195

=Gun=, action at muzzle, 27
annealing a gun ingot, 57
assembling of, 48-54
arquebus of, 1537, 47
barrels, erosion of, 35
blow-holes, 56
bore searcher, 59
breech of a, 53
discharges, force of, 33
calibre of a, 53
elastic limit, 58
elongation, 58
forging a (illus.), 52
heat treatment, 58
hoops of a, 54
improvements in, 45
ingot, calibre of, 55
jacket of, 54
length of a, 53
liner of, 54
life of, 35
manufacture in America, 48
measuring inside diameter (illus.), 59
modern built-up (illus.), 54
mold for ingot, 55
muzzle of, 53
pressure generated in a big gun, 54
photography (illus.), 33
piping, 56
powder chamber of a, 53
rifling (illus.), 60
rifling of, 53
shrinking pit, 59
tensile strength of, 58
factory, testing materials, (illus.), 50
tube of, 54
tube, how it is tempered, 57
why called gatling, 310
wire-wound, 54

=Gun-barrels=, imported from England, 49
resisting pressure of, 34

=Gun-cotton=, in smokeless powder, 35, 206

=Gunpowder=, Chinese probable discovers of, 44
discoverer of, 44
experiments by Schwartz, 45
formula of Roger Bacon, 45
ingredients in, 205
manufactured in monasteries, 44
what causes the smoke? 206
smokeless, what made of, 206
why some is fine and others large grained, 206

=Gurgle=, in bottles, 63

=Hail=, what causes, 124

=Hair=, what causes baldness, 143
why it don’t hurt when cut, 143
why it keeps growing, 144

=Hand bombards=, early types, 45

=Hands=, shaking, why with the right, 231

=Hansom=, why so called, 122

=Have= plants fathers and mothers? 175

=Heart=, why beats during sleep, 191
why beats faster when scared, 191
why beats faster when running, 191

=Heat=, light wave changed into, 36
why a nail gets hot when hammered, 230
why some things are warm, 144
how we obtain, 231

=Hemp=, Manilla (illus.), 356

=Hobson’s choice=, how originated, 311

=Honey=, apiary in summer (illus.), 534
how produced, 527
worker comb (illus.), 532
manner of using German bee-brush, 533
finished product (illus.), 533
frame (illus.), 535
how to bump the bees off a comb (illus.), 533
bee-hat (illus.), 535
a study in cell-making (illus.), 532
bee sting, can a, 536
frame of bees (illus.), 535
comb, how bees build, 536

=Honey-bee=, poison-bag, 537
egg of queen, under microscope (illus.), 529
preparing for rearing, 531
living on combs in open air, (illus.), 527
the daily growth of larvæ (illus.), 532
effect of a sting (illus.), 536
worker-bee (illus.), 527
what the queen-bee does? 528
drone-comb (illus.), 532
clipping queen bees wings (illus.), 533
cucumber blossom with bee on it (illus.), 528
queen-bee (illus.), 527
the queen and her retinue (illus.), 529
queen-rearing, 531
queen-cells (illus.), 529

=Honeymoon=, why do they call it a? 311

=Horizon=, how far away is the, 245
what is it, 244
where is it, 244

=Horse-power=, a, what it is, 256

=Horseshoes=, why it is said to bring good luck? 311

=Hot box=, cause of, 368

=Houiller=, French gunsmith, 48

=Houses=, concrete (illus.), 101

=How= far does the air extend? 243
is ammunition made (illus.)? 49
does an arc light burn? 307
are automobile tires made? 382
does a honey bee live? 336
does a bee make honey? 527
do bees build the honey comb? 536
does the honey bee defend itself? 536
does honey develop in a comb (illus.)? 530
do birds learn to fly? 178
do birds find their way? 407
does the blotter take up the ink of a blot? 18
this book is bound, 578
this book is made, 561
the paper in this book is made, 561
the pictures in this book are made, 581
are bullets made? 51
is an ocean cable laid? 429
does a camera take a picture? 22
is a cable dropped into the ocean (illus.)? 432
are modern carpets made? 169
is a carpet woven by machinery? 171
is china decorated? 406
is china made? 404
is chocolate made? 392
did the custom of clinking glasses in drinking originate? 232
are cigars made? 517
is cloth made from wool? 86
did the coal get into the coal mines? 257
does a coal mine look inside? 260
do the cocoa beans grow (illus.)? 391
is the color put on the outside of the pencil? 469
is the honey comb made? 532
are concrete roads built (illus.)? 103
did man learn to cook his food? 308
are concrete buildings made (illus.)? 100
is woolen cloth dyed? 87
big is the earth? 124
much of the earth does the sun shine on at one time? 324
does an elevator go up and down (illus.)? 396
was electricity discovered? 333
does the light get into the electric bulb? 305
is the eraser put on a pencil? 469
can an explosion break windows? 62
explosions may occur on submarines, 278
does the farmer use concrete (illus.)? 102
do our finger prints identify us? 520
did man learn to fight fire? 308
did man learn to make a fire? 289
are fishes born? 177
was the flag made? 310
is flour made? 462
does a fly walk upside down? 454
did men learn to fly? 126
does the gas get into the gas jet? 302
is illuminating gas made? 303
is gas purified? 303
is plate glass made? 246
is plate glass ground? 250
a wire-wound gun is made? 54
was the first American gun made (illus.)? 47
is a gun ingot made? 55
do we find the length of a gun? 53
is a gun tube tempered? 57
do we obtain heat? 231
the heel of a shoe is put on (illus.), 560
did Hobson’s choice originate? 311
far away is the horizon? 245
does a key turn a lock (illus.)? 491
does a spring lock work (illus.)? 492
are lead pencils made? 467
do the miners loosen the coal? 261
is light produced, 230
are magnets made? 335
are matches made? 293
are match boxes made? 294
did man learn to send messages? 412
does the meter measure the gas? 304
can microbes spread through the body? 410
are mirrors silvered? 522
big is a molecule? 348
did money originate? 455
are moving pictures made? 369
does the music get into the piano? 478-482
did the word news originate? 312
did a nod come to mean yes? 19
did shaking the head come to mean no? 19
are paints mixed? 228
is a photograph developed? 23
was the piano discovered? 479
do plants breathe? 241
do plants reproduce life? 175
does the shield cut through the ground in tunnel building? 212
are shooting shells photographed? 24
shoes are made by machinery, 549
shoe machinery was developed, 457
is crude rubber secured? 377
is rope turned and twisted? 358
are rubber tires made? 378
are modern rugs made? 169
to splice a rope, 364
do men go down to the bottom of the sea? 202
did the sand get on the seashore? 108
far back does the silkworm date? 109
was silk introduced into Europe? 110
are the silkworms cared for? 113
do we know a thing is solid, liquid or gas? 348
are sounds produced? 485
fast does sound travel? 486
can sound come through a thick wall? 79
is the volume of sound measured? 242
far does space reach? 256
do the slate pickers work? 259
does a captain steer his ship across the ocean? 407
can a ship sail under water, 269
is a submarine submerged? 270
do sponges grow? 286
do sponges eat? 287
are sponges caught? 287
are the stars counted? 241
big is the sun? 141
hot is the sun? 141
is a steel pen made (illus.), 17
did man learn to shoot, 40
do we get wool off the sheep? 82
is a stone thrown with a sling? 41
are metallic and paper shells filled with powder? 50
did man learn to talk? 18
did the telephone come to be? 70
fast does thought travel? 242
does a telegram get there? 414
did man learn to tell time? 313
did man begin to measure time? 314
did men tell time when the sun cast no shadows? 317
is the time calculated at sea? 315
is tobacco cultivated? 516
is tobacco cured? 516
was tobacco discovered? 512
is tobacco harvested? 515
is tobacco planted? 514
is a tunnel dug under water? 208
does water put fire out? 222
is white lead made? 225
are wires put under ground? 76
did writing first come about? 11
did the Chinese write? 13
did the Monks do their writing? 14
does a pen write? 18
much does the wool in a suit of clothes cost? 83
much wool does America produce? 82
is wool taken from the sheep? 82
is the yarn for carpets dyed? 170
is oxide of zinc obtained? 226
does the water get into the faucet? 501
are the big water pipes laid? 504
did the name Uncle Sam originate? 458

=Human body=, wonders of the, 311

=Hunting=, with the bow-and-arrow, 43

=Hurt=, why we cry when, 93

=Hydrogen=, what it is, 349

=Hypo=, used in developing, 23

=Impact=, of projectile from guns, 28

=Ink=, how does a blotter take up? 18

=Instruments=, artillery, testing, 24
musical, 488
optical, based on refraction, 38

=Incandescent lamp=, development of, 306

=Inside= of a mine planting submarine (illus.), 277

=Iron=, cast, 265
melts at, 35
the most valuable metal, 265
wrought, 265

=Is= a moth attracted by a light? 288
man an animal? 180
the hand quicker than the eye? 376
there a reason for everything? 200
there a man in the moon? 400
yawning infectious? 192

=Jacket=, of a gun, 54

=Japan= the natural home of the silk worm (illus.), 112

=Kentucky rifles=, 45

=Key=, how it works in a lock (illus.), 491

=Knots=, different kinds of (illus.), 363
what makes, in boards, 223

=Lambs=, Siberian, in South Dakota (illus.), 80

=Lamps=, first street light in America, 296
the Clanny safety, 264
did candles come before? 294
earliest forms of, 295
Edison’s first (illus.), 306
incandescent carbon (illus.), 306
incandescent, development of, 306
incandescent, electric, when invented, 305
French watch tower (illus.), 295
Mazda (illus.), 306
from Nushagak hanging (illus.), 297
Pagan votive (illus.), 296
Tantalum (illus.), 306
street, when first used, 295
chimney protects flame, 37
coal miners and safety, 262

=Lamp chimney=, why it makes a better light, 37

=Langley, Dr. Samuel P.=, 1914 flight of aeroplane, 128

=Languages=, why so many, 197

=Lantern=, the first oil (illus.), 297
the “Réverbère” (illus.), 297

=Laugh=, when glad, why we, 92
nerves, 93
when tickled, why we, 93

=Laughter=, reflex action, 93

=Lead=, as used in making paint, 267
in a pencil, 468
why so heavy, 267
as used in pipes for plumbing, 267

=Leather=, how the hides are treated, 539
treatment of hides, 538
unhairing machine (illus.), 540
hide house (illus.), 538
tanning process, 539
rolling room (illus.), 539
tanning sole leather, 539
how upper leather is tanned (illus.), 540
disposing of waste material, 540
wringers, 539
tan yard (illus.), 539

=Legs=, not same length, 91

=Lens=, in the eye, 22

=Leyden jar=, what it is, 332

=Life=, beginning of, 174
beginning of man’s, 174
how plants reproduce, 175