PART I

I

A PATHWAY OF CEMENT

"I do wish papa would buy the land from Mr. Breigel. The weather will

soon be fine enough to play out of doors!"

So said Jessie Gregg, a rosy-cheeked girl of twelve, to her eldest

brother, Fred, one evening in March, as they stood in the porchway of

their home, situated near the bank of the Passaic River, a few miles from

the city in which Mr. Gregg had his business offices.

"Why, Jessie," said Fred, "papa told me this morning, at breakfast, he

expected to close the deal, that is, get the deed of the property, this

afternoon. I am just as anxious as you are to have the matter settled,

for if he gets the land, I will have a lot of work to do, and I want to

commence it right away. The land must be ours, for papa is later than

usual this evening. Oh! there's the train just coming in; he will be here

in a few minutes, and then we'll know."

"Oh, Fred! he and George are coming now. I see them at the turn of the

road. I'll run to meet them." Away she scampered, and almost upset her

father by jumping into his arms, as she was quite a plump, husky girl and

evidently a pet, for her father kissed her fervently as she slid from his

arms to the ground. Then the three trudged homeward.

"Jessie," said George, a younger brother, "I have a secret for you if you

won't tell Fred, until papa has told him."

"What is it?"

"Papa has bought the land, and has got it in his pocket."

"Oh! I am so glad," said Jessie, "but how can he have it in his pocket."

"George means that I have there the papers, deeds, conveyances, and

receipts, giving me the sole ownership of the land, and all that is on

it, including the trees, old barn, and other structures; so, girlie, you

can get down to the river now without having to climb a fence."

Fred met his father on his arrival at the house, but was too well behaved

to ask him about the land, though he was as anxious to know as he could

be. His father saw the boy's anxiety and after tea asked him to go with

him into his den, a little room nicely fixed up some time previous,

containing many articles of wood, brass, and plaster of Paris, Fred and

George had made during the past winter. Jessie, also, had contributed many

little things toward the decoration of "the lion's den," as she called

the room into which her father retired to have his evening smoke, to take

a friend, or to do a little private business.

When seated, Mr. Gregg called Fred to his desk, and talked over some home

affairs before he said: "Now, my boy, since I have secured the property

behind us, as you children desired, I shall expect you and George to help

by your labour, and by the knowledge you obtained at the training school,

in making the improvements on the land and the water front we have talked

of so often. I am sure, with my advice and assistance, you will be able

to do most of the work, or at least to superintend it in such a way that

the labour and expenditure will not be wasted. You know, Fred, I am not

a rich man, so cannot afford to waste money on experiments."

"Indeed, father," said Fred, "I will do all I can. You may count on my

giving my best attention to whatever work and improvements you entrust me

with."

"That is well said, my boy, and what I expected from you. We will begin

operations by putting down a cement pathway from the walk now leading to

the house from the street, and continue it to the river, where you must

build a small boat house and workshop, as I intend either to purchase a

small gasoline launch for our own use, or have you build one, if you feel

equal to that."

"Oh! father, you are so good," said Fred. "There is nothing I'd like

better than to do this work, and particularly to build a boat. I'm sure

I can do that with your help and advice. As to putting down the pathway,

that I can do very well, after my good training in cement works."

"All right, my son. We'll see in the morning what old material we have

on the two places which can be used. There must be quite a quantity of

lumber, timber, bricks, hard mortar, and plaster in and about the old barn

and the smaller buildings."

The next morning George evidently had something on his mind, and seemed

to be on the point of explosion. Mrs. Gregg noticed this and said to

him, "Why are you so restless this morning? Why don't you finish your

breakfast?"

"Oh! mother," he exclaimed, "I am too glad. I am so full of the good

things Fred told me last night and this morning I haven't any room for

breakfast."

"What did Fred say to you?" asked the mother.

"Oh! he told me he was going to build a cement walk right from the door

here to the river, and do lots of other things; and best of all, mother,

he is going to build a boat, a real boat, that will be driven by a

gasoline engine, just like Walter Scott's. That will be glorious! I can

take you and Jessie up the river to Belville to see aunty, whenever you

want to go."

"Very well, George; we will see about that after the boat is ready to take

on passengers."

Breakfast over, the whole family walked out to see the newly acquired

property. They had all seen and walked over the grounds often, but never

before with that feeling of pride in ownership which possession creates.

As there could be no objection to the removal of the line fence between

the newly acquired property and the homestead, Fred got a handsaw, and cut

down a part of it, making an opening some nine or ten feet wide, so that

all could pass into the new place without climbing or stumbling.

The old barn was the first thing examined, and it was found to be in a

state of good preservation, and quite large. It had been built--perhaps in

Colonial times--of heavy timber, oak, chestnut, and pine, and it contained

enough timber and lumber to build two or three small cottages. There

was a big pile of broken bricks and mortar lying against one side of the

barn; and another large pile of bowlders, or field stones, near the fence.

"These," Fred said, "will be fine to build a little landing place or pier

for the boat. The broken bricks and hard mortar will make grand stuff for

the foundation of the cement pathway."

There were also two or three small buildings on the place. One had been

used for a poultry house, another for a tool house, and a third seemed

to have been a sort of cattle shed. Mr. Gregg suggested their removal, of

which all approved.

There were quite a number of good-sized trees on the grounds, and these

rendered it a little difficult to set out a straight line to the river

for the cement walk, without cutting down several, which could not be

considered. There was one direction, however, that would admit of a walk,

about four feet wide, but there were some big rocks or bowlders in the

way, that would have to be removed before a straight path could be made.

Still it was decided to put it there.

"The rocks," said the father, "can be removed by blasting, by lifting

them out of their beds and rolling them aside, or moving them down to the

river, where they will form a good protection against both current and

ice."

"I think they can be moved," said Fred, "if I can get levers and rollers;

and they will make fine breakwater stones."

Jessie found two suitable trees, upon which Fred promised to put up a

strong rope swing, as soon as the place could be cleaned up and made tidy.

"Now, Fred," said the father, "this cement walk should be commenced at

once, so that it will be dry and hard before you go on with other work. I

will employ a labouring man to help you, one who will do the heavy work,

as I do not want you to over-exert yourself. You have a number of tools

now in the shed, and, when I come home from the office this evening, we

will make out a list of the other tools and materials you will require to

finish the intended work. In the meantime you and George can be making

a number of wooden stakes, about eighteen inches long and two inches

square. Point them sharply at one end so that they may be driven into

the ground their whole length. You will require thirty or forty of these.

After getting them, take a clothes line, old halyard, or any rope or heavy

string your mother can find for you, and stretch it from the house down to

the river, at the point we decided upon. Drive in a stake near the river,

tie one end of the rope to it, pull tightly, and stretch the rope from the

river to the house. It will then show you where one edge of the walk is

to be. After that is done, get another rope or string and, starting from

the house end of the walk, measure off four feet for the proposed width.

Drive in a stake at that point, and tie one end of the second rope to it;

then go toward the river with the other end, making the rope extend the

whole length of the path and drive in another stake which must be four

feet from the first rope. To this stake tie the end of the rope and make

it tight. Be sure to have the two ropes exactly four feet apart at each

end, as well as along the whole length. You will find it to your advantage

to get a straight strip of wood, say, one or two inches thick both ways,

and cut it exactly four feet long. It can then be used as a measuring

stick or gauge, for the distance between the ropes, which is to be the

width of the walk, and by using it you will have a parallel and uniform

path from start to finish."

Mr. Gregg had passed an examination in the Massachusetts School of

Technology, and had won a position as civil engineer in New York which

later he abandoned for the profession of law; hence his knowledge of

practical mechanics and engineering.

After Jessie and George had gone to school, Fred started on his new

undertaking with enthusiasm. He found quite a number of pieces of wood,

out of which he made over forty stakes, and pointed them nicely with the

large hatchet he always kept sharp and in good order. By tying several

pieces together, it did not take him long to find cord enough to set out

the whole walk. An old halyard that had been taken from the flag pole

and replaced by a new one answered the purpose admirably. Driving a stake

into the ground, near the house, he tied one end of his cord to that, and

stretched it down to the river bank to the point chosen for the end of

the walk, where another stake was driven in and the cord tied to it. The

long stretch between the two stakes would not allow the cord to be tight

enough to make a straight line between the two points, but Fred left it

as it was, to be adjusted when his father came. With his rod he measured

off four feet from the first stake, across the intended path, and drove

in another stake to which he attached another cord. Then going down to

the river he measured off the width of the walk from the long cord, and

drove in another stake. He was now ready to have his father examine the

work he had done, and to make suggestions or changes if such were deemed

necessary.

Jessie and George arrived home from school, having run most of the way,

"to help Fred make the walk," and were quite disappointed to be told there

was nothing they could do until the work was further advanced.

"We might, perhaps, commence taking down the old buildings," said Fred,

"and pile the lumber where it will be snug and dry."

"All right," said George; so the three of them went over to the poultry

house and Fred began by taking out the two or three small windows, and

removing the doors by unscrewing the hinges. George's desire to pull,

tear, and smash the old material was held in check by Fred, who advised

him to be careful, and not break or destroy anything that could be used.

After the doors had been taken off and laid nicely away--"to be used on

the boat house"--and the windows and frames placed in a dry spot, Fred

began to remove the old siding, or clapboards. He found this a rather

difficult job, as they were nailed on with old-fashioned wrought-iron

nails which could not readily be drawn, and, in trying to get the boards

loose, the ends kept breaking and splitting; so he stopped, went inside

the building, and took off the lining there; this also was a little

difficult to do, but, as the boards were an inch thick, he did not split

many of them.

He then sawed off the boards alongside the studs, on the corners, and

at the doorways to relieve the siding at the ends, and give him a good

chance to wedge off the boards wherever they were nailed. With the help of

George, he succeeded in getting most of them loose without serious damage.

Of course, he had to begin tearing the boards off at the top of the wall,

as they lapped over each other like the scales of a fish.

Mr. Gregg arrived, went over the ground, and was well pleased with the

results of Fred's day's work. He assisted in straightening the long

cords, and made a number of suggestions for the boys to follow. He had

a strong-looking man with him, who he told Fred was to help him. He was

an Italian, named Nicolo, called "Nick" for short, a kindly fellow, who

could speak English fairly, for he had been employed in Newark, as a handy

labouring man for years. He, Fred, and George soon became good companions,

and even Jessie, though a little shy at first, soon became quite friendly

toward him. When it was explained what was wanted of him, he was quite

satisfied, and agreed to begin work in the morning.

Next day Fred and George were at work before their father was out,

and soon Nick arrived, bringing a spade, a crowbar, and a pick. He was

immediately set to work by Fred, digging a shallow trench for the pathway,

a little over four feet wide and about eight inches deep. The stretched

cord and the four-foot rod were the guides.

[Illustration: Fig. 1. Section of sidewalk]

There were a number of rocks to be removed from the trench, one of them

near the river bank weighing over a ton. These were left to be removed

later. Their father, on coming out, was glad to see them all at work; he

showed Fred and Nick how to prepare the edges of the trench by putting

planks along them, as shown in Fig. 1. The boards, about twelve inches

wide, and from twelve to sixteen feet long, had been taken from the old

barn.

After breakfast Fred worked along with his man, and got the trench well

cleaned out, except for a few of the larger rocks. The smaller bowlders

were wheeled down to the river and rolled over the bank to the water's

edge. Near one side of the walk grew a large tree, whose main root ran

under the proposed path. Mr. Gregg had noticed this in the morning and had

told Fred to see that the root was cut off close to the line on both sides

and pulled out altogether. "If it isn't cut off, it will grow larger, lift

up the cement flags, and perhaps break them." Fred saw the force of this,

so had the root cut off and taken out. The operation would not kill the

tree, though it might do it some injury.

Now came the process of taking out the big stones, and a lever, ten or

twelve feet long, was brought from the barn, in the shape of a red cedar

pole, five or six inches in diameter at the larger end. Nick took an axe

and chopped the big end a little flat on two sides, so that it could be

shoved under the stone. A flat plank was next laid behind the stone on

the ground, on which a fulcrum was to be placed, in order to get what

is termed by workmen a "purchase." On the side of the stone next to the

river, three planks taken from the floor of the barn were laid down flat

at the bottom of the trench. Three other planks were laid on the top of

the first layer, thus making a bed in the trench, two planks in thickness,

on which the big stone was to be rolled. A fulcrum, consisting of an old

fence post, was laid upon the plank, and forced up as close to the stone

as possible. Everything was now ready for lifting the bowlder out of the

bed, where it had lain perhaps for thousands of years.

As had been arranged, the work at this stage was suspended, and other

work gone on with, until Mr. Gregg made his appearance. Upon his arrival

all hands went to the stone, Jessie included. Having approved what had

been done, the father suggested that rollers be placed between the two

thicknesses of plank to increase the ease of moving the stone to the river

when it was started. Fred and Nick went to the barn, and among a big pile

of old planks, boards, and timber found eight or ten old fence posts, six

or eight inches in diameter, and long enough to make two rollers, each

three feet long, when cut in two. These were quickly stripped of bark by

George and Jessie, while Nick and Fred, with axe and hatchet, soon had a

number of them round enough to serve as rollers. The father then directed

that the ends nearest the river, of the top layer of planks, be raised

up, and one of the rollers placed between the two layers of plank near the

stone, while the ends of planks nearest the stone should be left resting

on the bottom ones. Another roller was placed nearer the river end of the

planks, and all was made, as shown at Fig. 2--where fulcrum, lever, stone,

planks, and rollers may be seen.

[Illustration: Fig. 2. Raising rock with lever]

All was now ready; the lever was adjusted in place under the stone and

on the fulcrum. Mr. Gregg, Nick, and the children were gathered about the

lever, each one pushing down, and the stone began to move, as the top end

of the lever came down, much to the delight of Jessie and George, who kept

shouting, "There she goes! Up she goes!" Finally the great stone turned

over on the plank, and was moved to near the centre. Now came the labour

of getting the monster down to the bank. This was made easier by raising

the ends of the upper planks under the stone and inserting another roller,

five or six feet from the end. The planks holding the stone were now

resting on rollers, as seen in Fig. 3, and it was found easy to move, but

in order to get it to the bank of the river the "runway," or lower planks,

had to be laid down that distance; this would take too many planks, so it

was decided to lay only a second length on the ground, and then when the

load had travelled to this length, the plank behind the stone should be

carried forward and laid down again. This was continued until the load

was slid into the water. Mr. Gregg called the children and told them to

push against the stone, and they all were filled with wonder to see this

great stone move along so easily on the rollers.

[Illustration: Fig. 3. Moving rock on rollers]

Fred and Nick got more rollers to put between the planks as the stone was

pushed forward, for, of course, these were continually coming out at the

rear end of the loaded planks. The rollers had also to be watched and kept

square across the plank or they would slide, making it hard to move the

load.

When the river bank was reached, Fred and Nick made a rough slide of

old timber down to its side from the trench. Getting the lever properly

adjusted under the planks and stone, the latter was turned over on the

slide, when it plunged into the river with a great splash, causing the

water to fly and sprinkle each one of the workers, much to the delight of

George, who thought it fine fun to see his father, Fred, and Nick get a

wetting.

It was decided that the stone as it lay in the water should form the

end of the pier for the boat, as it was nicely situated and the proper

distance out, being about a foot out of the water at high tide. The other

stones were easily removed from the trench by Fred and his man, and were

either rolled or wheeled down to the river, where Nick built them as well

as he could on both sides of the big rock, leaving a hollow space between

the walls, to be filled in afterward with small stones, mortar, and broken

bricks, for the making of a good, strong boat pier.

Mr. Gregg then took out his note-book and pencil, and figured out the

quantity of cement, sand, and gravel required to complete the cement work.

He found there was good sand, clean and sharp, on one corner of the new

lot. A big pile of gravel and broken stones out on the street had been

left over from the building of a two-story concrete house nearby, so he

concluded to buy it, if not too dear.

Measuring the trench, he found it to be 300 feet long, by 4 feet wide,

making a surface of 1,200 feet to be laid with cement, concrete, and

gravel, or broken stones. He calculated that every 100 superficial feet

of the concrete walk would require about a barrel and a third of Portland

cement; and that the top dressing of cement and sand, or fine crushed

stone, required another third of a barrel; which totaled up to 20 barrels,

all told. The concrete to be used was to be proportioned as follows: One

part of cement, two parts of good, clean sand, and five parts of gravel,

or broken stones, which should be small enough to pass through a ring

having a diameter of not more than two inches. This mass should be well

mixed, dry, on a wooden floor or movable platform, and then wetted just

enough to have stones, sand, and cement, well moistened. All should be

again mixed before being placed in the trench, and it should not be thrown

in place, but shovelled in gently.

Mr. Gregg ordered the cement by telephone, to be delivered at once, either

in barrels or bags; and he got into communication with the owner of the

gravel, and bought the whole pile. He then engaged a team of horses,

wagon, and driver, to commence work the next day. By this time Nick had

gone home, and the children came rushing into the house, anxious to tell

their mother all the work they had done that day.

The keen appetites of the younger folks gave positive proof of their

having earned their supper, by actual work, and, when the meal was over,

the father invited Jessie and the boys into his little room. George was

asked to take with him his portable blackboard, some chalk, and a ruler,

and all marched into their father's den.

"Now," said Mr. Gregg, "I have often told you I would explain to you

some things about the mechanical powers, and this seems to be the most

appropriate time to begin, as you have fresh in your minds the application

of the lever as we used it to-day in raising and moving the big rock. I

am glad to see that Fred grasped the idea so readily, for that encourages

me to let him use his own judgment while doing this job.

"The lever is known to accomplished mechanics, as 'the first mechanical

power', and Archimedes said of it, if he only had one long and strong

enough, together with a suitable fulcrum, he could, alone, lift the earth

from its place.

"This Archimedes was a celebrated Greek philosopher and mathematician, who

lived from about 287 to 212 B. C. The discovery of the law of specific

gravity, which I will some day tell you about, is attributed to him. I

think George can tell you something about this great man, as I saw him and

Jessie the other day reading Plutarch's 'Lives,' in which he is mentioned.

[Illustration: Fig. 4. Principle of lever and fulcrum]

"A lever may be formed of any strong, stiff material, wood, iron, steel,

or similar stuff, and it may be of any length, or dimensions, according

to the purpose for which it is to be used. In theory, it is supposed to

have no weight, and is simply figured as a straight line having neither

breadth nor thickness. In practice, however, a lever may be a handspike,

a pry, a crowbar, a fire poker, a windlass bar, or any other appliance

or instrument that can be used for prying. While we may not know the

proper name of the little steel tool the dentist employs when preparing

one's teeth to receive the filling, by cleaning out the cavities, we are

safe in calling it a small lever. When your mother stirs the fire in the

grate, she makes a lever of the poker, and bars of the fireplace become

fulcrums. The fulcrum is the fixed point on which the lever rests when

in use. The force applied is called the power and the object to be acted

upon is called the weight. The spaces from the power and the weight,

respectively, to the fulcrum, are called the arms of the lever. There

are three different ways of using the lever, according to the relative

positions of power, weight, and fulcrum. This rough sketch I am drawing

on the blackboard (Fig. 4) shows the lever being used to raise one end of

a heavy stone. Suppose W is a big rock, C will be the fulcrum, B the end

of the lever under the stone, and O the power. The weight thrown on the

lever by the man at O, raises the stone so that it can be blocked up, the

lever and fulcrum arranged for another lift, and the process repeated.

This can be continued until the stone is raised to the height required,

or until it is turned over. This method applies to the raising of any sort

of weight, engine, boiler, heater, etc.

"In this sketch the distance from B to C shows the short arm of the lever,

and the distance from C to O shows the length of the long arm.

"A lever, used in this way, is called a lever of the first kind, because

of its simplicity and easy adaptation to many purposes. I saw George

digging in the garden the other day, making a flower bed for his mother.

The spade he used formed an excellent lever. He forced it into the ground

to its full depth, pried the handle toward him, and broke loose the soil,

after which he turned over the earth in the bed. Now, in this case, the

top of the blade or foot-plate of the spade, rested on the hard ground,

which was the fulcrum; the soil dug up was the weight, and George's

hand at the top of the spade handle, furnished the power. I am sure you

all understand the working of a lever of this kind, but I will give you

another illustration.

[Illustration: Fig. 5. Lever as a mechanical power]

[Illustration: Fig. 6. Double lever as scales]

"Here's another sketch (Fig. 5), in which A,B,C, together show the lever,

also the power A, the fulcrum B, and the weight C. If I should place the

fulcrum B so that it would be in the middle between the ends A C, there

would be what is termed an equilibrium between the weight and the power,

and if they are equal there will be a perfect balance maintained. It is

on this principle that scales for druggists are made, the lever being

suspended in the centre of its length, as I show in the sketch (Fig. 6).

These scales are very nicely adjusted, and the chains and receivers are

made as nearly alike in weight as possible. The arms of the lever being

of equal length from the centre, or pivot, permit the lever to stand in a

perfectly horizontal position, unless disturbed by having a weight placed

in either one or other of the receivers. In this case, the pivoted point

P is the fulcrum, and the two points O and X may be taken as the power

and the weight. If one pound is placed in the receiver at O, it will

tip the scale down, and that will become the weight, while any commodity

placed in the receiver at X, until the lever is again brought level, or

horizontal, may be called the power. As another illustration I'll tell you

of something that took place the other day. In the vacant lot are several

piles of bricks, stones, and planks. George, seeing this, took one of the

planks and threw it across several others, making a 'Teeter Tauter,' or,

as some children call it, a 'Seesaw.' He balanced the plank nicely, and

then invited Jessie and her cousin to sit on it, one at each end. The two

girls were about the same weight, and George held the plank until both

were seated. It remained level and balanced, until George got on the top

of it, and stood on the centre of its length, placing his feet so that one

was on one side of the centre, or fulcrum, and the other on the other. By

causing his weight to rest on his right foot, the right end of the plank

would dip downward; then by throwing his weight on his left foot, the

movement of the plank would be reversed, and the motion continued until

George ceased to exert any extra pressure on either of his feet. What do

you call the boy or girl who stands on the plank?"

"Sometimes," said Jessie "we call him a 'candlestick' and sometimes 'the

balancer'."

"This teeter tauter and the explanation of the druggist scales," said

the father, "show you that many of our conveniences are due to the lever

in one way or another. These are but a few of the thousands of instances

I could name. Take a nut-cracker, for instance. There we have a sort of

double lever, the joint being the fulcrum, the nut the weight, and the two

handles the combined power or lever. By pressing the handles or levers,

we crack the nut or overcome the weight, by crushing it. We owe many of

our amusements to the lever in one form or another. Even our pianos would

be impossible were it not for the combination of levers in the adjustment

of the keys. Machinery and all kinds of moving instruments, including

watches, clocks, and other fine mechanism, could not be perfected without

the lever. The common every-day wheelbarrow is a good illustration of

the use of the lever combined with the wheel. George fills up his barrow

with stones or other materials that weigh two or three times the amount

he could lift easily. Yet he gets away with the load, apparently with

very little trouble. The handles form the lever or power, the wheel the

fulcrum, and the stones the weight. George raises the handles, and throws

the greater part of the weight on the fulcrum, which is the wheel, and

this latter, acting as a roller, is easily moved around its own axle, thus

enabling George to move his threefold load with ease.

"This example shows you how, by a simple combination of mechanical

devices, labour may be reduced. The roller is related to the wheel and

axle class--another of the mechanical powers.

"In your bicycles you have a fine illustration of the application of the

roller principle, in the ball-bearings. The little round balls, over which

the axle of the wheel runs, are simply rollers rounded in every direction,

and placed there to destroy friction, which they do almost entirely.

"Another excellent illustration of the use of the roller is seen in the

hanging of the grindstone we have in our back shed. The axle passing

through the stone rests on two pairs of wheels or rollers, one pair at

each side of the stone. If you turn the stone on its axis, you will notice

the wheels turn also, and the effort required to turn the stone is hardly

noticeable. If the grindstone were well balanced and true, and the little

wheels the same, so that they could be run without friction on their

bearings, the stone, by giving it one good turn with the hand, would keep

revolving a very long time. So you see how much we are indebted to the

mechanical powers for our present state of civilization."

Next morning being Saturday, George was up early, put on a pair of

overalls his mother had bought, and, when breakfast was over, all but the

mother went out to the new property. They found Nick helping a teamster

to unload gravel, also a load of cement, which was placed in a dry and

convenient place, for once damp or wet in the least it becomes of little

use, unless worked up immediately. George was full of glee. He got his

wheelbarrow and wanted to commence work without delay. The father took

Fred and Nick to the trench and explained what was to be done and the way

to do it. "The trench is now eight inches deep," he said, "and you must

wheel gravel, broken bricks, hard mortar, or cinders into it so that there

will be about five inches of it in the trench from one end to the other.

Put all the larger stones at the bottom, but before throwing in any, tamp

or pound the ground at the bottom of the trench until it is solid and

hard, making a good bottom for the stones to rest on, and ensuring the

walk from settling or sinking in spots. Where the big root and rocks are

taken out, the holes must be filled up level, and tamped solid. Rake off

the largest of the gravel, and let George wheel as much of it as he can,

and dump it in the trench, while Nick or you wheel in the balance. Finish

the top of the gravel off with smaller sized stones, and after you have

filled in about five inches, throw water on the whole with the garden hose

until quite wet, and then pound the gravel down until it is compact and

firm. This bed forms a good foundation for the concrete which must be laid

on it about four inches thick, and well tamped.

"After you have raked off the larger gravel, take a wire sieve, with

meshes not larger than four to the inch, and sift the finer gravel out,

to save for the top finish. Before filling in the concrete, strips of wood

having straight edges on top must be nailed to the stakes on both sides of

the walk, as I showed you on the blackboard in Fig. 1, marked A A. These

strips must be placed at proper grade in their length, and level across

from one to the other. A straight edge made of wood, and long enough to

reach over the walk, and the strips as well, must be provided, and it may

be notched out as I show at X, in Fig. 1. This straight edge is to be used

in levelling off the top or finishing coat, by keeping both ends on the

strips A A, and moving it along lengthwise of the walk. If the top of the

walk is to be below the edges of the strips, you may notch the ends, as

shown, to suit whatever depth may be required."

Fred told his father he thoroughly understood the process as far as

explained, and the latter then left. By this time Nick and George--and, we

might add, Jessie--had wheeled into the trench quite a lot of gravel, but

for the want of a proper "tamper" they had to stop. So Fred cut two pieces

off a fence post, each about a foot long, and with an auger or boring

tool, made a hole in the centre of the end of each, about eight inches

deep, into which he inserted a round wooden handle, about three feet long.

These made excellent "tampers," not too heavy for George to use. Jessie,

persuaded Fred to make her "just a little one," but he told her not to use

it much or her hands would get sore and too stiff to practise her music.

The strips for the stakes were prepared, nailed on, and properly adjusted,

and then it was time to commence the real work. Nick had nailed some

boards on three pieces of scantling about six feet long, which made a

good mixing table for the concrete. This was carried up near the top end

of the walk, and placed where it would be handy. A pailful of cement was

put on the board, next two pailfuls of nice clean sand, and then five

pails of gravel that had no stones in it larger than would pass through

a ring having a clear diameter of two inches. All this gravel, sand, and

cement being in one heap on the board, Fred and Nick worked at it steadily

for more than ten minutes, mixing it up until the sand and cement were

thoroughly and evenly blended with the gravel. Fred then sprinkled the

mixture with clean water from the hose, while Nick kept shovelling it over

and over until the whole was damp, but not so much so that the cement and

sand were washed from the gravel. The whole mass looked like a pile of

dirty stones that had just been under a light shower.

"This," said Fred to Nick, "is a very important process, for if we make

the stuff too wet, it will starve the concrete by washing away the cement,

and if we leave it too dry the work will be rotten and crumble away."

Fred might also have added that the proper proportioning of the materials

was as essential as the proper mixing, and in this case, where we

are making it one of cement, two of sand, and five of gravel--all by

measurement--we must adhere closely to the rule or the walk will be uneven

in texture and colour.

The concrete being properly mixed, Fred and Nick began to shovel it into

the trench, spread it to about four inches in thickness, and tamped it

down until the top mass looked sloppy and muddy. While in this condition,

a new lot of cement mixture was made, consisting of one part of cement

and two parts of sand and the fine of the gravel that had been sifted.

All were mixed thoroughly while dry, and afterward wet to the consistency

of thick mortar. This was spread over the concrete to about one inch in

thickness and levelled down by the notched straight edge until the proper

thickness and level were obtained. The surface was then ready to smooth,

or "float," as the workman calls it, which always gives to the top of

the work a nice, even, level appearance, and makes it solid and firm. The

"floating" is done with a tool made of wood, as shown in Fig. 7, and may

be finished off with a plasterer's steel float, merely to give the surface

a better finish.

[Illustration: Fig. 7. Floats and trowels]

The floating operation is laborious, for it must be done at once, while

the operator is on his knees. Fred and Nick, however, worked away at it

until they made a good job of the portion that they were putting down. All

of the walk they could finish at one time was about sixteen or eighteen

feet, so that the whole job required a number of days to complete.

The first instalment being done, so far as the floating was concerned,

it was now in order to make joints in the walk across the face, firstly

for the purpose of marking it off into flag sizes, four feet square;

secondly to prevent expansion. If there were no joints made in the walk,

it would "lift" up, crack, break, and ultimately be destroyed. Fred, who

knew that the walk would contract in cold and expand in warm weather,

explained this peculiarity to George and Nick, and having a "jointer"

along with the floats which the father had sent, he, with Nick's help, ran

some joints, at four-foot intervals, across the walk, while Nick pushed

his spade through the joints to the ground, actually cutting cement and

concrete into sections of four feet each. This would allow for expansion

or contraction, and even admit the raising of some of the sections above

the others, without cracks or breaks occurring.

The first instalment of the walk being made, it was left to George to

wheel damp sand and scatter it over the face of the walk about an inch

thick, to keep the sun and rain from injuring it.

Then he received instructions to wet the surface every morning for a week.

At the end of two or three days the cement was hard, or "set" enough to

bear walking on, and in a week it was cleaned off for use. One peculiarity

about concrete or cement work is, that it improves and gets stronger with

age.

The walk was complete in due time, in sections of about sixteen feet

long, and proved quite satisfactory. Mr. Gregg was pleased with it, and

he explained to Fred, George, and Jessie that it might have been made

more ornamental, as there were many tools for rounding off the edges,

indenting the surface, to make it less slippery, or for laying the flags

off in panels; but in this case all were pleased with the way the boys

had finished it.

II

BUILDING OF A BOAT HOUSE

The cement walk being finished to the satisfaction of all concerned, and

the admiration of the neighbours, Fred turned his thoughts to the building

of a boat house and workshop. It was decided to make it 16 feet wide and

22 feet long, as these dimensions would suit the timbers in the old barn,

and be ample for stowing away the boat and allowing space for a work

bench.

Lines for a foundation were set out, and stakes driven in the ground

at the corners, alongside the cement walk and pier. A trench about two

feet deep was dug on the two sides and ends; and in this were laid large

rocks and stones, in a single course all round. Nick, who was quite handy

at this kind of work, built up a wall of smaller stones laid in cement

mortar. This mortar was composed of one part of cement to five of sand,

and made quite thin and easy to spread. When the wall was high enough,

about level with the highest part of the ground, it was levelled off by

using smaller stones and plenty of cement mortar. The level was obtained

by laying a straight plank flat on the top of the cement finishing, and

then applying an ordinary spirit-level. Any errors in the level of the

wall showed at once, and were made right by adding more mortar, or by

taking some off the top of the wall.

[Illustration: Fig. 8. Framing studding]

Timbers from the old barn were next pressed into service, chestnut wood

that had served as girths and beams. Two pieces were cut, 22 feet long,

and two of 16 feet. The ends were then halved, as shown in Fig. 8--the

simplest method of framing a corner--and the timbers were spiked and so

squared as to make right angles at the corners.

Fred then took the old window and door frames, and measured off on the

foundation timbers the outside distance where each one was to be placed.

He put the double doors in the end of his boat house, next to the river

front. The other door and windows were set in the best places to provide

an entrance opening on the cement walk, light above the work bench, and

views over the river and grounds. Fred decided to build his house ten feet

high; so a quantity of studding, 2 × 4 inches in section, was taken out

from the walls of the barn, and cut exactly ten feet long. These were to

form the side walls between the corners, doors, and windows. Heavier studs

were found in the barn, and Fred wisely used them next to the windows and

doors.

[Illustration: Fig. 9. Side of boat house frame]

These heavy studs were set up in the places marked on the timber sills,

also at the four corners, and were toe-nailed at the bottom to hold them

in place. They were then made vertical or plumb, by aid of a spirit-level,

and the corners were braced temporarily to hold them in that position. The

picture (Fig. 9) shows how the side of the building next to the cement

work looked when the studding was all in place. The dark ends shown are

the joists on which the floor is laid. The lower joists were made from

timbers taken from the barn floor, 2 × 8 inches wide and long enough

to reach across the building. The joists on top were 2 × 6 inches, by

16 feet long. These latter floor beams were set about 15 inches apart,

ready to receive the flooring plank, which was nailed solid to them. You

will notice that cross pieces of studding are nailed between the studs

at the window openings. These form the tops and bottoms of the window

frames. The spaces above and below are also filled in with short pieces of

studding, to nail the clapboards to, as shown. The ends of the building

were finished as shown in Fig. 10, a small window being left in each to

admit light and air, also lumber, poles, or other stuff that could be put

into the loft through these openings. Inside the building a trapdoor was

to be left, so that Fred or George could get up to take in or hand out

the stuff.

[Illustration: Fig. 10. End of boat house frame]

The end (Fig. 10) shows how Fred and Nick, with George's help, built

that portion, the collar beam, O O, and the rafter being seen, while the

details in Fig. 8 give larger sketches of the manner of doing the work.

The stone-work, as built by Nick, for foundation walls, is shown in both

Figs. 9 and 10.

All the clapboards having been taken off the barn and old sheds, the

better portions were selected for covering the outside of the new frame,

and a lot of old boards were used for lining the inside of the walls and

nailing on to the rafters. The next thing was to lay on the shingles.

These had been provided some days before by Mr. Gregg, who had figured out

the number required. He found the roof would measure 24 feet in length,

including the projections over the ends of gables, and that the length of

the rafters was 17 feet each, including the overhanging eaves or cornice.

This made the whole stretch of length on both sides of the roof 34 feet.

Multiplied by 24 feet, the length of the roof, this was 816 feet. To

cover an area of 816 feet about 8,000 shingles would be required, as 100

surface feet require nearly 1,000 shingles, laid 4 inches to the weather,

according to the usual custom. Mr. Gregg explained to Fred what is meant

by the term "weathering," applied to shingles, clapboards, slates, or

anything similar. The "weathering" part of a shingle is that portion of it

exposed to the weather, when in place on the roof. It makes no difference

how wide or how narrow a shingle may be, it is that portion showing from

the lower end of one shingle to the lower end of the next one above it,

that is the "weathering." This is generally four inches wide and it runs

from end to end of the roof. Another thing Mr. Gregg explained--the term,

"a square of shingling." "In this case, as in flooring, clapboarding or

similar work, a square is an area 10 × 10 feet; or 100 superficial feet.

In nailing down shingles," went on Mr. Gregg, "the nails should be driven

so that the next course or layer will cover up the nail heads, thus

protecting them from rain and damp, and preventing them from rusting. When

laying the shingles, after the first courses are on, which should be laid

double at the eaves, a string or chalk line must be stretched from one

end of the roof to the other, four inches up from the ends of the first

courses. This string or chalk line may first be rubbed over with chalk or

soft charcoal, and when drawn tight from each end, it may be 'struck' or

'snapped' by raising it up in the middle and letting it strike the roof

suddenly so that a mark will be left on the shingles from end to end. This

will be the guide for the thick ends of the shingles to be laid against

when nailing on the next course, and the process must be continued until

the ridge, or top of the roof, is reached. When you paint your boat house,

don't forget the roof, for a good coat of paint on the shingles will

lengthen the life of the roof fully five years."

Fred, to whom these instructions were more particularly given, told his

father he understood the whole matter, and he was directed to go on with

the work. In the meantime the father ordered the shingle-nails required;

five pounds for each thousand shingles, or forty pounds altogether.

The building being small, the whole work was soon completed, windows put

in, doors hung, and floors laid; and Mr. Gregg was greatly pleased with

the manner in which Fred had managed the job.

[Illustration: Photograph by Frank H. Taylor

BOAT HOUSE AND WORKSHOP

"A Good Coat of Paint on the Shingles Will Lengthen the Life of the Roof

Fully Five Years."

]

The next thing was to take down the heavy timbers of the barn, still

standing. Fred saw at once that they were too heavy to be removed without

mechanical aid or more human help, so he brought from his father's stable

a rope and set of pulley-blocks like the ones shown in Fig. 11. Nick,

who had seen some service at sea, hooked the block into a loop formed by

a short piece of rope tied over a limb projecting from one of the trees.

The question of lifting the timber now was an easy one, as another short

rope was tied to the heavy post W, in this case the weight P being the

power. Each of the blocks shown contains pulleys which make the relation

of the weight to the power as one to four. The weight being sustained by

six cords, each bears a sixth and a weight of six pounds will be kept in

equilibrium by a power of one pound. The blocks used in a system of this

character are called single if there is one pulley in each, double if

there are two, treble if there are three, and quadruple if there are four.

Fred, George, Nick, and Jessie who liked to help whenever she could,

counted for four times their number when they all pulled together on the

rope P. It was astonishing to the youngsters how easily the heavy timbers

were taken down and piled in a nice heap.

Two timbers, each about twenty-five feet long, were chosen and marked, to

be used for slides or ways, on which the proposed boat could be hauled in

and out of the boat house. It was quite a distance from the timber to the

river end of the boat house, and, the former being heavy, Fred decided

to make an inclined plane of planks--of which there was an abundance--so

that the timbers could be slid or rolled down to the river. It took but

a few minutes to lay the planks, and as the incline was gentle, rollers

were used and the timbers went down as easily as the big rock had done.

This pleased the younger children very much.

"When papa comes home," said Jessie, "I'm going to get him to tell me

about the 'inclined plane' as well as the ropes and pulleys."

The two timbers were rolled into the river and floated to the boat house,

where one end of each was raised to the floor level at the doorway and

made fast; the other end sank to the bottom, where Nick dug down and made

a bed for it to rest in. These beds were made deep enough to bury the

ends, and large stones were then thrown in to keep them from moving, but

these were not allowed to reach within 18 inches of the surface of the

water, which was then at its lowest mark. The timbers were kept about

three feet apart, ample space to admit of any ordinary launch or row boat

being taken into the boat house.

"Oh, Fred," said Jessie, "do you think those two sticks will be strong

enough to hold the boat while you are pulling it up?" "Why, yes; strong

enough to hold a dozen boats no larger than the one we intend having made.

I don't know how much weight these timbers will support, nor how heavy our

boat will be with the engine in it, but I'm sure the timbers are strong

enough."

Jessie's question, however, caused Fred to think over the matter, and

he set to work to find out how to tell the strength of timber beams. He

discovered that to be able to determine the strength of beams and wooden

pillars under all sorts of conditions required considerable training in

mechanics and mathematics, but that the case before him was comparatively

easy. A general rule for finding the safe carrying capacity of wooden

beams of any dimensions, for uniformly distributed loads, is to multiply

the area of section in square inches, by the depth in inches, and divide

their product by the length of the beam in feet. If the beam is of

hemlock, this result is to be multiplied by seventy, ninety for spruce

and white pine, one hundred and twenty for oak, and one hundred and forty

for yellow pine. The product will be the number of pounds each beam will

support. For short-span beams, the load may be increased considerably.

Fred, who had some knowledge on the subject, acquired at the training

school, determined to pursue his studies in this direction.

In talking over the matter of nails with his father, their holding power

was mentioned, and Mr. Gregg told Fred of a test that had been made some

time ago by the U. S. Ordnance Department, where cut and wire nails had

been tested respectively, showing a decided superiority for the former,

both in spruce, pine, and hemlock. Thus in spruce stock nine series of

tests were made, comprising nine sizes of common nails, longest 6 inches,

shortest 1-3/8 inches; the cut nails showed an average superiority of

47.51 per cent.; in the same wood six series of tests, comprising six

sizes of light common nails, the longest 6 inches and the shortest 1-1/8

inches, showed an average superiority for cut nails of 47.40 per cent.;

in 15 series of tests, comprising 15 sizes of finishing nails, longest

4 inches and shortest 1-1/8 inches, a superiority of 72.22 per cent.

average was exhibited by the cut nails; in another six series of tests,

comprising six sizes of box nails, longest 4 inches and shortest 1-1/4

inches, the cut nails showed an average superiority of 50.88 per cent.;

in four series of tests, comprising four sizes of floor nails, longest

4 inches and shortest 2, an average superiority of 80.03 per cent. was

shown by the cut nails. In the 40 series of tests, comprising 40 sizes of

nails, longest 6 inches and shortest 1-1/8 inches the cut nails showed an

average superiority of 60.50.

Speaking of the ropes used in blocks, while taking down the old barn

timbers, Mr. Gregg suggested that it would not be a bad idea if the boys

were taught a few general items concerning hempen ropes; so he asked them

to memorize the following: A rope 1/4 inch in diameter will carry 450

pounds, and 50 feet of it will weigh one pound. If 5/8 inch in diameter,

it will carry 3,000 pounds and 7 feet will weigh one pound. When a rope is

3/4 inch in diameter, it will carry 3,900 pounds, and 6 feet will weigh

1 pound. A rope one inch in diameter, the same as we have in our blocks,

will carry 7,000 pounds, and 3 feet 6 inches will weigh one pound. "It is

not likely that sizes greater than these will ever be used by you. If they

are, you can obtain a fair knowledge of their strength by finding their

areas, and comparing them with the areas of the ropes given, taking the

rope having one inch in diameter, as a constant example."

Wire ropes are much stronger than hempen ones, whether made of steel,

brass, or bronze. The care and preservation of ropes is deserving

of consideration, particularly in localities where the atmosphere is

destructive to hemp fibre. Such ropes should be dipped when dry into a

bath containing 20 grains of sulphate of copper per gallon of water, and

kept soaking in this solution some four days, before they are dried. The

ropes will thus have absorbed a certain quantity of sulphate of copper,

which will preserve them for some time, both from the attacks of animal

parasites and from rot. The copper salt may be fixed in the fibres by a

coating of tar or by soapy water. In order to do this the rope is passed

through a hot bath of boiled tar, drawn through a ring to press back the

excess of tar, and suspended afterwards on a staging to dry and harden.

The figures given are intended for new manila ropes, and do not hold good

for ropes made of inferior hemp. It is always safer never to load a rope

to more than 60 per cent. of its capacity, and not even this much when it

is old and weathered.

Jessie reminded her father of his promise to give them some information

regarding the power of blocks and tackle and the qualities of the inclined

plane. Accordingly, Fred, George, and Jessie joined their father in his

den after supper, and George placed his blackboard in a convenient place

with chalk, rule, and other requisites.

When all were seated, the father said: "Some time ago I tried to explain

to you the uses of the lever in quite a number of different situations;

to-night I'm going to show you how the various ropes and pulley blocks

are made to do service for mankind. These devices are used very generally,

especially in building operations, where heavy beams, girders, or blocks

of stone have to be raised. On board ship, it is the favourite mechanical

power by which rigging is raised, cords and ropes tightened, and goods

lifted from or lowered into the hold.

[Illustration: Fig. 11. Blocks and tackle]

"The pulley, the main feature of the third mechanical power, may be

explained almost on the same principle as the lever, as you will see upon

examining the sketch (Fig. 11) I now make on the blackboard.

"The pulleys seen in the blocks around which the rope runs may be

considered so many levers whose arms are equal, and whose centres are

fulcrums.

"In describing this power, it will perhaps be better to begin with the

first and simplest form of the combination. The pulley, weight, and rope

I show now (Fig. 12) is the simplest form of making use of this power. It

is called a snatch-block and often employed for drawing water from wells,

or for hoisting light weights. It is very handy, but we do not get any

additional power from it, though we get a change of direction and quick

movement. From its portable form, its low cost, and the handiness with

which it can be applied, this arrangement is one of the most useful of

our mechanical contrivances.

[Illustration: Fig. 12. Theory of block and tackle]

"When pulleys are adjusted, as I show you in this sketch (Fig. 13), the

block which carries the weight is called a movable pulley, and the whole,

as shown, a system of pulleys.

[Illustration: Fig. 13. Double block and tackle]

"In this illustration, suppose the weight is 20 pounds. It is supported

by two cords, A and B; that is, the two sections of the cord support 10

pounds each. Now, the cord being continuous, the power must be 10 pounds.

"We leave out of consideration the weight of pulley and the friction of

the various parts.

"We have seen that the weight is sustained by two cords; if, therefore,

it has been raised two feet, each cord must be shortened two feet. To do

this, the power P must run down four feet. To get the full value of this

machine the cords must be parallel.

"If we increase the number of movable pulleys, as sketched at Fig. 14, to

three, the relation of P to W will be as 1 to 8 and the distance through

which P will travel will be eight times that through which W is raised.

[Illustration: Fig. 14. Multiple blocks and tackle]

"If we apply this principle to the sketch (Fig. 11), which illustrates

the blocks you used to-day in lifting the large timbers, and which is

the usual form of pulley employed to lift heavy weights, you will notice

that there is a four-sheave block at the top, and a three-sheave block

at the bottom, with the end of the rope fixed from the top block. The

three-sheave block is movable. A power of 10 pounds will, with this form

of pulley, balance a weight of 60 pounds.

"Suppose a block of stone weighing 8,000 lbs. is to be raised to the top

of a wall and we use a system of pulleys where each of the two blocks has

four pulleys; we shall find that it will require a power of 1,000 pounds

to raise it.

"Now, as to the inclined plane: this is called the fourth mechanical

power, and it is not in any way related to the lever, but is a distinct

principle. Some writers on the subject reduce the number of mechanical

powers to two, namely, the lever and the inclined plane. The advantages

gained by this are many for just so much as the length of the plane

exceeds its perpendicular height is an advantage gained. Suppose A B C

(Fig. 15), I make in the sketch, is a plane standing on the table. If

length A B is three times greater than the perpendicular height C B then

a cylinder at R P may be supported upon the plane A B by a power equal to

a third of its own weight. That is, a block of that weight would prevent

the roller or cylinder from going farther. From this we gather that one

third of the force required to lift any given weight in a perpendicular

direction will be quite sufficient to raise it the same height on the

plane; allowance, of course, must be made for overcoming the friction,

but then, you see, you will have three times the space to pass over, so

that what you gain in power, you will lose in time. We see the use of the

inclined plane every day we pass a building under construction, where the

workmen wheel bricks, mortar, and other materials from the street to the

floors above, using long planks for the plane or tramway. Merchants, too,

often make use of an inclined plane when rolling heavy boxes and packages

from the street to the floors of their warehouses.

[Illustration: Fig. 15]

"An excellent, practical illustration was given you to-day when Nick and

Fred built the ways on which the proposed boat is to be slid into the new

house. It would require five or six strong persons to lift the boat bodily

into the new house; but I expect two or three will easily slide it up into

the building on the ways; and by arranging a winch--another mechanical

contrivance--at one end of the boat house, Fred, or George, for that

matter, will be able to haul the boat up. The winch for this purpose will

be a very simple affair, merely a ready adaptation of the wheel and axle,

as I will show you later. Now, however, we are talking about inclined

planes, and to illustrate its early application to the building arts, it

is only necessary to tell a few things we know regarding the moving and

raising of the great stones used in building the Pyramids. For centuries

it was a mystery how the heavy stones in these structures had been placed

in their present positions. Recent investigations have led many scientific

men to believe the stones were taken up inclined planes, on rollers, and

then put in place by the workmen, who moved them to the different sides of

the building on strong timber platforms, where rollers, or rolling trucks,

carried the load. According to one authority, there are the remains of the

approach to an inclined plane near the Great Pyramid, which, if continued

at the angle, as now seen, would rise to the apex. According to this

writer, the foot of the plane was more than a mile from the building,

fifty or sixty feet wide, and had been one huge embankment, formed of

earth, sand, and the clippings and waste of stone made by the workmen.

This, of course, would be an expensive and a tedious method, but in those

days time and labour went for little. Every time a course of stones was

laid and completed, the plane was raised another step, to the height of

the next tier of stones. The same angle of incline was probably maintained

during the whole period of erection, and this angle, you may rest assured,

was made as low and easy as possible; for the Egyptian engineers were not

slow in adapting the easiest and quickest methods available.

"This method of conveying the heavy stones to their places in the Pyramids

was simple and effective, with no engineering difficulties that could

not be readily overcome. Moreover, it was really the very best method

considering the narrow limits of their appliances.

"You may ask, 'How were these big stones carried to the foot of the

inclined plane?' The quarries, in some cases, were five hundred miles

distant, and most of the stones had to be brought across the Nile to the

works. We know from the monuments, and from the papyrii that have come

down to us from remote periods, that many of the stones were brought down

the river on large rafts or floats, and on barge-like vessels; and we

also know that many of the larger ones were hauled or dragged down from

the quarries at Assowan to Memphis, alongside the river, a distance of

580 miles. This is particularly true of the obelisks, for all along an

old travelled road evidences have lately been found that these stones had

been taken that way, and that resting places for the labourers had been

provided at stations about twelve miles apart, along the whole distance.

It has been estimated that a gang of men--say forty--well provided with

rollers, timbers, ropes, and necessary tools, could easily roll an obelisk

like that in Central Park, New York, twelve miles in twelve hours; and

doubtless this was the system employed in conveying those immense stones

that great distance.

"A large number of obelisks were erected near Memphis, though there are

none there now, for the Greek and Roman engineers, at the command of the

rulers, took a number down and carried them to the city of Alexandria;

but we have less knowledge of how these later engineers transferred the

stones to the newer city, than we have of the methods of the older. The

beautiful column known as Pompey's Pillar was once an obelisk, and was

transformed into a pillar, by either Greek or Roman artisans, it is not

clear which. The work of putting those huge stones in place was not easy,

as Commander Gorringe discovered when he stood the New York obelisk in

the place it now occupies.

"But let us get back to our inclined plane.

"I have shown you how a weight or roller acts on the incline, but I did

not explain it clearly, nor in a scientific way, as I do not want to

puzzle or confuse you with terms and problems you cannot understand. I

will, however, give you another illustration or two on the subject, in

which another factor plays a part, namely--gravitation. Let us suppose

you have two golf balls laid on a table that is perfectly horizontal or

level in every direction; they will remain at rest wherever placed, but

if we elevate the table so that the raised end is half the length of the

top higher than the lower end, the balls will require a force half their

weight to sustain them in any position on the table. But suppose they are

on a plane perpendicular to the table top, the balls would descend with

their whole weight, for the plane would not contribute in any respect to

support them; consequently they would require a power equal to their whole

weight to hold them back. It is by the velocity with which a body falls

that we can estimate the force acted upon it, for the effect is estimated

by the cause. Suppose an inclined plane is thirty-two feet long, and its

perpendicular height sixteen feet, what time should a ball take to roll

down the plane, and also to fall from the top to the ground by the force

of gravity alone? We know that by the force of attraction or gravitation,

a body will be one second in falling sixteen feet perpendicularly, and as

our plane in length is double its height at the upper end, it will require

two seconds for the ball to roll down from top to bottom. Suppose a plane

sixty-four feet in perpendicular height, and three times sixty-four feet,

or one hundred and ninety-two feet long; the time it will require a ball

to fall to the earth by the attraction of gravitation will be two seconds.

The first it falls sixteen feet, and the next forty-eight feet will be

travelled in the same time, for the velocity of falling bodies increases

as they descend. It has been found by accurate experiments that a body

descending from a considerable height by the force of gravitation, falls

sixteen feet in the first second, three times sixteen feet in the next;

five times sixteen feet in the third; seven times sixteen feet in the

fourth second of time; and so on, continually increasing according to the

odd numbers, 1, 3, 5, 7, 9, 11, etc. Usually, the increase of velocity is

somewhat greater than this, as it varies a trifle in different latitudes.

In the example before us we find that the plane is three times as long

as it is high on a perpendicular line; so that it will take the ball to

roll down that distance (192 ft.) three times as many seconds as it took

to descend freely by the force of gravity, that is to say, six seconds.

"The principle of the inclined plane is made use of in the manufacture of

tools of many kinds, as in the bevelled sides of hatchets, axes, chisels

and other similar tools, the examples of which are in a great measure

related to this power, though many of them partake largely of the wedge,

of which we shall now have something to say.

[Illustration: Fig. 16. Action of the wedge]

"The wedge may be a block of wood, iron, or other material, tapered to a

thin edge, forming a sort of double inclined plane, =A P B=, (Fig. 16)

where their bases are joined, making =A B= the whole thickness of the

wedge at the top. In splitting wood as is shown in the illustration, =R R=

being the wood, the wedge must be driven in with a large hammer or heavy

mallet which impels it down and forces the fibres of the wood to separate

and open up. The wedge is of great importance in a vast variety of cases

where the other mechanical powers are of no avail, and this arises from

the momentum of the blow given it; which is greater beyond comparison

than the application of any dead weight or pressure employed by the other

mechanical powers. Hence, it is used in splitting wood, rocks, and many

other things. Even the largest ships may be raised somewhat by driving

wedges below them. Often, in launching a vessel, wedges are used to start

it on its way. And they are also used for raising beams or floors of

houses where they have given way by reason of having too much weight laid

upon them. In quarrying large stones, it is customary to wedge or break

off the rock by first drilling a number of holes on the line of cleavage.

Wooden wedges are then driven tightly into these and left there until

they get wet, when they expand and split off the rock as required. This

method of quarrying large stones was well known to the old Egyptians, and

employed by them in quarrying their famous obelisks.

"Owing to the fact that the power applied to force a wedge is not

continuous, but a series of impulses, the theory of the wedge is less

exact than that of the other mechanical powers. Considering the power and

the resistance on each side, however, as three forces in equilibrium, it

may be demonstrated that the

Resistance (R) equals P × Length of equal side/Back of wedge

Then the mechanical advantage will be--

R/P equals Length of equal side/Back of wedge

So that by diminishing the size of the back and increasing the length of

the side--that is, diminishing the angle of penetration--the mechanical

power of the wedge is increased. While I did not intend to inflict you

with arithmetical or algebraical formulæ, I have been compelled to give

you that simple example which I know you can all work out, as it is

concise, and the same would be long and tedious if rendered in text."

Next morning, as Fred and his father were out on the new place early,

looking over the boat house, the slide for the boat, and some other

matters, Mr. Gregg suggested that a winch be placed at the upper end of

the house, to haul the boat out of the water. He also suggested that Fred

prepare for work on the boat at once, and provide himself with all the

tools and materials necessary. He promised to call on a friend of his

in the city, who is a noted boat builder, and ask him the best method to

adopt in building the craft.

"Perhaps," said the father, "it might be a good plan to buy a full set

of shapes or patterns from some one of the professional boat builders

who advertise such. They are sold at a very low rate--being made of

paper--and many firms sell all the material that is required to build

a boat complete; with the sweeps, ribs, and curved stuff cut out to the

required shape and numbered all ready to set up.

"What we want, Fred," continued the father, "is a boat sixteen or

eighteen feet long, just the size of the one belonging to your friend,

Walter Scott; that is plenty large enough for all our purposes. His

boat can stand as a kind of a model for you to work after in case you do

not thoroughly understand the patterns you are to get, or the manner of

arrangement. The gasolene motor we'll order from some manufacturer, with

whom we'll arrange to install it, with a suitable propeller and necessary

attachments."

Fred was quite satisfied with all his father had said and started to

get ready. Jessie began to question him about several things she did not

fully understand in her father's talk the night previous. Fred explained

matters, made them quite clear to her, and then asked her to get her

memorandum book and write down the following, which he said, she would

often find useful: "There are six mechanical powers, two of which father

has not told us about, but will no doubt do so, before long. These are

called, the Lever, Pulley, Wheel and Axle, Inclined Plane, Wedge, and

Screw. The Screw and the Wheel and Axle, you have yet to hear about. Now,

study carefully the following rules:

"_The Lever._--Rule: The power required is to the weight as the distance

of the weight from the fulcrum is to the distance of the power from the

fulcrum.

"_The Pulley._--A fixed pulley gives no increase of power. With a single

movable pulley the power required will equal half the weight, and will

move through twice the distance. Increasing the number of pulleys,

diminishes the power required. Rule: The power is equal to the weight,

divided by the number of folds of rope passing between the pulleys.

"_The Wheel and Axle._--Rule: The power is to the weight as the radius of

the axle is to the length of the crank or radius of the wheel.

"_The Inclined Plane._--Rule: The power is to the weight as the height of

the plane is to the length.

"_Wedge._--Rule: Half the thickness of the head of the wedge is to the

length of one of its sides as the power which acts against its head is to

the effect produced on its side.

"_The Screw._--Rule: As the distance between the threads is to the

circumference of the circle described by the power, so is the power

required to the weight."

Fred told George also to copy the foregoing in his memorandum book, so

that he would be able to work out any problems for himself.

III

BRIDGE AND BOAT WORK

The next day Fred and his father talked over the proposed boat, the result

being that Walter Scott was asked over the telephone if he would come down

in his launch to the Gregg property in the evening, as Mr. Gregg and Fred

would like to see the craft, hear all about it, and find out if it had

any defects that might be avoided in the building of another one. Walter

said he'd be glad to sail down, and would take his sister to see Jessie.

In the meantime some addresses of boat builders were handed to Fred, with

instructions to write and ask for catalogues, prices of materials, and

the other information usually sent out to prospective customers. Fred

immediately wrote to a number of firms, including several who manufactured

motors and other requisites for small launches.

A little after the city clock struck four, Jessie, who was home from

school, saw _The Mocking-Bird_ sailing down the river at good speed, with

Walter, his sister Grace, and their mother on board. Fred went down to the

water's edge, and helped Walter haul the boat to the unfinished landing

place, where Mrs. Scott and Grace were safely landed.

Fred and Walter soon became deep in "boat talk," and kept it up until

the arrival of Mr. Gregg, who began to make inquiries regarding the

speed, capacity, and safety of _The Mocking-Bird_. All his questions were

intelligently and favourably answered by Walter, a bright and earnest

little fellow. He was some months the senior of Fred, but was not so

strong or robust looking.

"She's just 18 feet long over all," said he, "with a 5-foot beam, a draft

aft of about 18 inches, and a forward draft of 1 foot. She is fitted with

a 6-horse-power gasolene engine, and her speed is from 8 to 9 miles an

hour."

An illustration of her, as she appeared when partly built, is shown in

Fig. 17, where a plan and a section of her length may be seen. The manner

of her construction is also shown, also the lines of ribs, portion of

inside lining, position of motor, rudder, and propeller.

[Illustration: Fig. 17. Plan and section of _The Mocking-Bird_]

Mr. Gregg also ascertained from Walter that his father had sent to a firm

who made a business of preparing the complete wood-work for many kinds of

boats on the "knockdown" system, selling the whole material ready to set

up without the aid of an expert. Printed instructions came along with

each boat, so that the buyer would have but little difficulty in setting

up the wood-work and making it ready for use. An expert workman had been

engaged by Walter's father to install the engine, line up the propeller

shaft, and connect the wheel and shaft to the engine. On the arrival of

the materials--within a week after the order was sent--Walter had gone to

work; and inside of fourteen days, _The Mocking-Bird_ took to the water.

So fully and so satisfactorily did Walter explain to Mr. Gregg all that

he asked about, that Fred was able at once to order the material for a

similar launch, to be sent on immediately. In order to hurry matters, a

cheque was inclosed with the order, and Fred, Walter, and George walked

over to the postoffice with the letter, so that it went by the night mail.

On returning, it was suggested that the boys, Grace, and Jessie go for a

sail on the river, and all were soon at the landing. Walter adjusted his

engine and made all ready as George and the girls got on board, while

Fred cast off the rope which held the boat to the dock, then stepped

after them. The engine was started, Fred took the tiller, and they were

soon afloat, sailing with the tide in their favour at a rapid speed,

and returning to the landing place inside of an hour, well pleased with

their little outing. Fred showed Walter his new boat-house and workshop,

explained to him how Nick and he, with the help of George and the advice

of his father, had completed the work and the building. He also pointed

out other work he was going to do as soon as his boat was finished.

Though not yet dark, it was getting rather late, and Walter's mother

advised that they start for home as soon as he was ready. So wishing Fred

every success in the building of his boat, Mrs. Scott, her daughter, and

Walter left for home.

"Well, Fred," said Mr. Gregg, when his family were all seated in the

living room, "you are now in for quite a job, one that will test your

working qualities; but I am sure you will come out with flying colours.

You will meet difficulties, but you must overcome them, and when the boat

is finished, painted, and ready to name, you can have some of your friends

up for the launching. Mother will have a special tea for you all, and

we'll christen the new craft. Meantime we must think over the matter of

a name, and decide upon one we shall all like."

Next morning, Fred and his father went down to the river's edge to examine

the little ravine that had been cut out by the spring and fall freshets.

It was a small affair, only about six feet deep and ten or twelve feet

wide. At present, the opposite side was reached by crossing a couple of

planks, safe enough while the land had been in a measure unoccupied. To

leave it so now would be a different matter, as Jessie or her mother,

attempting to cross, might easily fall over; so it was decided to have a

foot-bridge built over the creek, which was nearly dry the greater part

of the year. There was plenty of material on the ground for the purpose,

and Fred was asked by his father to get Nick to help, so that the bridge

might be ready as soon as possible.

Fred felt he was getting to be quite an important person when his father

trusted him with work which must necessarily entail considerable expense,

but he accepted the responsibility with pleasure, and promised to commence

at once, so as to have it finished by the time the material for the boat

arrived. So, when Nick arrived, operations began immediately.

[Illustration: The Creek]

Taking a tape line, Fred sent the Italian to the other end of it, and they

picked out a favourable location to measure across, making it over 11 feet

at the narrowest spot from one edge to the other. Allowance was then made

for bearings five feet on either side of the span, so that timbers 21 feet

long would be required to cross the chasm. This width would require three

string-pieces, or chords, to run across, one on each side, and one in the

centre. These, covered with three-inch plank from end to end, would make

a good, solid deck sufficient for all purposes. The planks were cut off

seven feet long, to have the deck of the bridge, over all, exactly seven

feet wide.

Among the timbers taken from the old barn were nine pieces, measuring 22

feet in length, 8 × 10 inches in section, so Fred decided to make use of

three of these just as they were, without cutting, and to place them on

their edges to get the most strength out of them. He then had six posts

cut off the old cedar fence posts, about two feet long, which were sunk

into the ground their whole length, as shown in Fig. 18, three on each

side of the creek, and the tops made level, so that a flat timber or plank

would rest on them, touching each one. This plank was made nine feet long,

so as to project over the posts about a foot at each end. This was, of

course, the same at each end of the bridge. After the flat timbers had

been laid on the ends of the posts and fastened with spikes, there were

laid the three long timbers spanning the gully. The spaces between were

equally divided, and then covered with three-inch planks taken from the

floor of the old barn. The boards were cut off to the proper length and

fastened down on the three timbers with spikes five inches long, the

planks not laid close together, but kept about three-eighths of an inch

apart, in order to let the water run off after a rain, as well as to allow

air to circulate underneath and between the joints to prevent the planks

from decay.

[Illustration: Fig. 18. Frame of foot-bridge]

In order to make the bridge safe, it was necessary to build a rail on each

side. Two pieces of timber about 20 feet long and 6 × 6 inches square were

used for the rails, while posts and braces were made of timber of about

the same dimensions. The bottoms of the posts were halved, so that they

could be spiked or nailed to the long outside string-pieces, as shown in

the illustration. Tenons were made on the top of these posts, and these

fitted into mortises made in the top rails, and all were then put together

and fastened with wooden pins.

Nick dug away the surplus earth from the approaches to the bridge, and

made an easy grade to its deck. This completed the work all but the

painting, which was left to be done some other day.

Mr. Gregg inspected the bridge, pronounced it all right, and congratulated

Fred on his workmanship, at the same time saying a good word to Nick and

George, both of whom had helped very much to make the effort a success.

In the evening Mr. Gregg told Fred and George that a friend of his had

given him a copy of the rules to be observed when running a launch, so he

asked the boys to get their note-books, and take these down as he read

them out. Even Jessie, too, he thought, ought to be acquainted with the

rules, as she might be called upon some time to make use of them, so three

pencils were soon at work, as the father read out the following:

"1. When at the wheel, remember as a first consideration, that you

cannot entertain the boat's occupants as well as steer.

"2. Keep your course, and know what that course is.

"3. Regulate your speed to the company you are in. Marine motors

are, as a rule, very flexible.

"4. Do not cut corners.

"5. When approaching a landing, learn to judge exactly the distance

your boat will travel after your propeller has stopped, so as to

run alongside without using your reverse gear. This requires some

practice, but is amply rewarded by time saved, in the long run,

and decrease of wear and tear on engine, gear, and propeller. Any

one can get to a landing in time by alternately running full speed

ahead and then astern.

"6. When aboard your boat, and facing the bow your right hand is

starboard, your left, port. Keep to the right. Should you be

overtaking any one, it is your duty to pass clear on their left.

The above applies only to narrow waters.

"7. When going up or down stream, should you wish to cross over to

the other side and return, and another boat is overtaking you on

your left, don't attempt to cross its bow; slow down until it has

passed.

"8. Keep clear of non-engined crafts. You have greater freedom

of action than they; it costs you nothing, and their occupants

appreciate your courtesy.

"9. Do not tow canoes or skiffs alongside. If towed at all, they

should be right aft with as short a towline as possible.

"10. Finally; remember the rules of the road--

"'Green to green or red to red

Perfect safety--go ahead

If to starboard red appear

'Tis your duty to keep clear.

When upon your port is seen

A steamer's starboard light of green,

There's not so much for you to do

As green to port keeps clear of you.'"

The children all promised to memorize these rules.

As the stuff for the boat was not expected for some days, Fred and Nick

kept at work about the new boat house, and building up the landing dock.

The former fitted up a work bench, and put his little shop in readiness

for actual use. Fred also hunted for a nice stick of timber among the old

barn ruins, on which to set up the boat. A good piece found, he cut it

to a length of 20 feet, and then he and Nick got it into the boat house,

where Fred planed it off a little with a rough jack plane, keeping a sharp

lookout for nails, sand, or gravel. Nothing destroys the cutting edges of

tools more than nails, bits of iron, glass, sand, or small pebbles, which

sometimes escape the vigilance of the workman. Especially is this true of

saws, which Fred knew quite well since he had once run a good sharp saw

against a nail, while cutting a piece of timber in two. This taught him a

lesson he never forgot, and whenever he had to cut up old material, he was

always careful to examine it all round, and to scrape or brush off all the

dirt and sand from the parts through which the saw teeth had to travel.

In planing, or "dressing" the stick of timber, the same precautions were

taken, and the surface of the wood was made as clean and free from dirt

and sand as it possibly could be. Notwithstanding all this, Fred found

it almost impossible to keep the cutting iron of his jack plane sharp

enough to take off shavings. He had to sharpen it every few minutes. This

is nearly always the case when working up wood which has previously been

used. However, he managed to "dress" his stick very nicely, and after

finishing it, laid it down along the middle of the floor of the shop,

putting blocks of wood under it here and there to raise it up from the

floor five or six inches. It was then made level on top and fastened down

so that it would not move or get out of line. This was about all they

could do on the boat until the materials arrived. Nick had managed to fill

in the space between the two walls of the little pier with heavy bowlders,

and had strengthened the whole with coarse rubble-stone work in such a

manner that there was little danger of injury from floating ice or flood

tides; and he had covered the whole over with small stones, gravel, and

a good thick layer of cement concrete, which made it correspond with the

cement walk.

The question of a winch was then taken up with Mr. Gregg and it was

decided to construct a simple affair at the end of the boat-house opposite

the large doors, where the boat would have to enter.

[Illustration: Fig. 19. Winch and crank]

Mr. Gregg suggested, in order to make the end of the building strong

enough, that two upright posts be set up, well braced by being fastened

to both floor and ceiling, and that the winch be attached to them in a

way that would be easy to work, as shown in Fig. 19, room enough being

left between the posts and the wall for the crank to turn without the

hand of the operator striking the boards. The cylinder around which the

rope should wind ought to be about six inches in diameter, and the crank

or handle on the end, not less than fifteen or sixteen inches long. The

longer the crank, the less force it would require to haul in the boat. If

desired, a crank could be fitted to the other end of the cylinder so that

two persons could work at one time, pulling in the weight.

In the evening Mr. Gregg asked the boys and Jessie to visit his room, and

he would try to explain the principle and advantages of the wheel and

axle, as the winch they were to make was in a measure related to that

principle. Mr. Gregg began by saying: "The wheel and axle is merely a

modification of the lever and consists of a couple of cylinders turning on

a common axis, the larger cylinder is usually called the wheel, the lesser

one the axle. This arrangement, which I draw on the blackboard herewith,

forms a kind of lever of the first or second class. Considered as a lever,

the fulcrum is at the common axis, while the arms of the lever are the

radii of the wheel and of the axle.

"The fulcrum is at C, the centre. The arm of the weight is W W, and the

arm of the power is A C. In Fig. 20 the arm of the power is the spoke of

the wheel, while the arm of the weight is the radius of the axle. Fig.

19 shows the ordinary winch, often used in well-digging for hauling up

dirt and rock, and also for raising planks, shingles, rafters, and other

light stuff, to the roofs and upper floors of buildings. Often it is made

more powerful by adding spur or geared wheels to the end of the shaft,

consisting of a pinion and a larger spurred wheel. The crank or handle

is attached to the pinion, and the power is increased according to the

difference in diameters of the spur wheels. The machine is then called a

'crab' and it is often used for lifting safes and other heavy weights to

elevated situations. In Fig. 20 the length of the crank (in a straight

line) is the arm of the power.

[Illustration: Fig. 20. Wheel and axle]

"The mechanical advantage of the wheel and axle equals the ratio between

the diameter of the wheel and of the axle.

[Illustration: Fig. 21. Capstan and hand bars]

"It is not necessary that an entire wheel be present. In the case of the

windlass and the capstan (Fig. 21), the power may be applied to a single

arm or to a number of arms placed in the holes shown. The cable or rope

on the barrel of the capstan is hauled in by turning the capstan on its

axis, with handspikes or bars. The capstan is prevented from turning back

by a pawl attached to its lower part, working in a circular ratchet on

the base.

[Illustration: Fig. 22. Compensating fusee]

"As an illustration of the lever action, and of work put into and got

out of a machine, there is no better illustration than the ingenious

contrivance termed the fusee (Fig. 22). In good watches and clocks, where

the elastic force of a coiled spring is used to drive the works, the

fusee compensates the gradually diminishing pull of the uncoiling spring.

The driving of the works at a constant rate is the object for which a

watch or clock is designed. This usually entails a constant resistance

to be overcome, but since one of the most compact and convenient forms of

mechanism into which mechanical force can be stored is that of the coiled

spring, and since the very nature of the spring is such that its force

decreases as it uncoils, we must employ some compensating device between

this variable driving force and the constant resistance. The fusee does

this in a most accurate and complete manner. As the fusee to the right is

to compensate for the loss of force of the spring as it uncoils itself,

the chain is on the small diameter of the fusee when the watch is wound

up, as the spring has then the greatest force.

"In the differential, or Chinese windlass (Fig. 23), different parts of

the cylinder have different diameters, the rope winding upon the larger

and unwinding from the smaller. By one revolution the load is lifted a

distance equal to the difference between the circumference of the two

parts.

[Illustration: Fig. 23. Chinese winch and pulley]

"There are many other contrivances and appliances of the wheel and axle

for performing various services, but I think the examples I have shown you

will be sufficient to enable you to make use of the device to perform any

duty you may be called upon to attempt in ordinary life, but, should you

enter professional life as civil, mechanical, naval, or mining engineer

or architect, you will be obliged to pursue the study of these subjects

further.

"Before closing I may add a few problems for you to solve at your leisure

by the application of the rules I have given you when describing the other

mechanical powers.

"The pilot wheel of a boat is 3 feet in diameter; the axle is 6 inches;

the resistance of the rudder is 240 pounds. What power applied to the

wheel will move the rudder? Here the difference between the axle and wheel

is 18 inches.

"Four men are hoisting an anchor of 3,000 pounds' weight; the barrel

of the capstan is 8 inches in diameter; the circle described by the

handspikes is 7 feet 6 inches in diameter. How great a pressure must each

of the men exert?

"With a capstan four men are raising a 1000-pound anchor; the barrel of

the capstan is a foot in diameter; the handspikes used are 5 feet long;

friction equals 10 per cent. of the weight. How much force must each man

exert to raise the anchor?

"The circumference of a wheel is 8 feet; that of its axle is 16 inches;

the weight, including friction, is 85 pounds. How great a power will be

required to raise it?

"A power of 70 pounds on a wheel whose diameter is 10 feet balances 300

pounds on the axle. Give the diameter of the axle.

"An axle 10 inches in diameter fitted with a winch 18 inches long is used

to draw water from a well. How great a power will it require to raise a

cubic foot of water, which weighs 62-1/2 pounds?"

The first mail in the morning brought word that the whole of the partly

prepared stuff for the boat had been shipped by "fast freight," and that

it would reach its destination in the course of a few days. The paper

patterns, directions, and all necessary instructions for building would

be mailed at once.

IV

MAKING A GASOLENE LAUNCH