Fig. 17, a Hindoo Picotah. where the stream that "River."

17. Ida. I have read, in an old book, of a curious method of raising water in Hindostan. It is called by the Hindoos a picotah. Here is a picture of it, which I think sufficiently describes itself, except that another person must stand by the well to empty the bucket.

Ella. We often see in the country a contrivance something like this, called a sweep, or a well-sweep. Ida. Yes; and there is one yonder, just at the foot of the hill, comes down from the glen enters our

well.

John. And many a draught of the purest water I have taken from the "old oaken bucket" that hangs there.

18. Frank. That old-fashioned sweep always reminds me of the first home that I knew, before I went to the city to reside, and of Woodworth's beautiful little poem, "The Bucket." How many times I have repeated that poem to myself when thinking of my early home.

Mr. M. Perhaps Master Frank will entertain us with a recitation of the piece, while Master George helps us to a practical illustration from the "moss-covered bucket" itself.

19.

20.

THE BUCKET.

How dear to this heart are the scenes of my childhood,
When fond recollection presents them to view!
The orchard, the meadow, the deep-tangled wild wood,
And every loved spot which my infancy knew;

The wide-spreading pond, and the mill which stood by it,
The bridge, and the rock where the cataract fell;
The cot of my father, the dairy-house nigh it,
And e'en the rude bucket which hung in the well!
The old oaken bucket, the iron-bound bucket,
The moss-covered bucket, which hung in the well.
That moss-covered vessel I hail as a treasure;

For often, at noon, when returned from the field,
I found it the source of an exquisite pleasure,
The purest and sweetest that nature can yield.
How ardent I seized it, with hands that were glowing,
And quick to the white-pebbled bottom it fell;

21.

Then soon, with the emblem of truth overflowing,
And dripping with coolness, it rose from the well;
The old oaken bucket, the iron-bound bucket,
The moss-covered bucket arose from the well.
How sweet from the green mossy brim to receive it,
As poised on the curb it inclined to my lips!
Not a full blushing goblet could tempt me to leave it,
Though filled with the nectar that Jupiter sips.
And now, far removed from the loved situation,
The tear of regret will intrusively swell,

As fancy reverts to my father's plantation,

And sighs for the bucket which hangs in the well;
The old oaken bucket, the iron-bound bucket,

The moss-covered bucket, which hangs in the well.

Mr. M. Both the poem and the illustration are excellent. All of you have doubtless seen both the common windlass and the chain-pump used for drawing water from wells and cisterns. But do you recollect, George, of a very ancient and singular invention for elevating water called the Screw of Archimedes ?

George. Very well indeed. It is said to have been used by the Egyptians in draining their land from the overflowings of the Nile. It consists of a hollow screw-thread wound round an axis, and is turned by hand or by machinery. The water continually rises through the spire, and is discharged from the top.*

22. Mr. M. These are but a few of the methods which the ingenuity of man has devised for elevating water. I am glad you omitted all the usual kinds of pumps, as they belong to a future lesson. Can you give me, Frank, a description of any kind of water-wheel for propelling machinery?

Frank. I have seen a mill driven by a large wheel called

*Fig. 19, the screw of Archimedes. To explain the mode of operation of this screw, suppose a small ball to be dropped into the mouth, A; it will roll down the tube until it arrives at the lowest

point, B. If the screw be now revolved, the point B will as

cend, C will come down lower than B, and the ball will

consequently roll to C. In one entire revolution it will

roll to D, and in a second to F; and in six
revolutions it will roll from the upper end
of the screw. If a quantity of water were
contained in the lowest spiral, it would be
carried up in the same manner as the
ball. Two of these screws may be
made to work simultaneously, and
to better advantage, round

the same axis.

an undershot wheel, placed in the current. The force of the current turns the wheel, which moves the machinery connected with it.

23. John. There is an old wheel of this kind at the foot of the cascade which we are just coming to, and that will give us a practical illustration.

George. Where the streams are small, rapid, and have sufficient fall, I have frequently seen mills driven by what is called an overshot wheel. The water falls upon the wheel, and by its weight, principally, turns it.

Frank. There is also a water-wheel, called the breast-wheel, which receives the water against the side of it instead of the top or the bottom. In this case the water acts partly by its momentum and partly by its weight.

24. Mr. M. Of these wheels the overshot is the most powerful; but both that and the breast-wheel require a considerable fall of water, while the undershot wheel, which is the least powerful, requires merely a strong current.

Ida. I have seen the experiments with what is called "Barker's mill," which is moved by the pressure of a column of water.*

25. Ella. Here is the cascade itself; and there, at the foot of it, is the old wheel which John spoke of! I understand now what an undershot wheel is.

Ida. And don't you see-where the water tumbles over that ledge another little wheel? That is a breast-wheel. How swiftly it spins round!

Ella. And there is still another and larger wheel lower down! That is an overshot wheel. It does seem as though some one has had all these wheels put up for the purpose of illustrating this lesson in hydraulics!

*Fig. 20, Barker's mill. In what is called "Barker's mill," the machinery is moved by hydrostatic pressure. It consists of a hollow clyindrical pipe, A B, of considerable height, terminating above in a funnel-shaped cavity, resting below on a pointed steel pivot, and communicating below with a cross tube, or arms, E F, closed at the extremities, but having openings on the opposite sides, near each end of the cross tube. A pipe, G, above, regulates the supply of water, and keeps the vertical pipe full.

If the openings at E and F be closed, it is evident that the hydrostatic pressure in the cross tube will be the same on all parts of its surface, and will be proportioned to the height of the pipe A B; but let the water flow at the orifices, and there will be more pressure on one side of the cross tube than on the other, and the machine will revolve in the direction of the greater pressure.

The movement of Barker's mill was long attributed, but erroneously, to the reaction of the jets (pressing upon the elastic air) against the extremities of the cross tubes. On the principle of hydrostatic pressure, as here illustrated, the turbine wheel has lately been invented. It is the most powerful and economical of all water-engines. See Fig. 21, next page.

26. All seemed to be of the same opinion; while Mr. Maynard only smiled, and said he hoped they would examine all the wheels, and be able to give a full description of them at another time. All were soon busy in clambering up the rocks, and noticing the working of the wheels; and after some time spent in this way, all returned to the foot of the cascade, when John described the new turbine wheel which his father had lately had put up in his mill, and which is moved by the action of the pressure of a column of water.*

"This wheel," said Mr. Maynard, " can be made to utilize from three fourths to four fifths of the theoretical power of the water, while the undershot wheel will not often give to machinery more than one quarter of the water power. The breast-wheel, when well constructed, will utilize a little more than one half of the moving power of the water, and the overshot wheel about two thirds."

Before the little party left this pleasant spot, Frank happened to remark that the numerous little water-falls in this cascade forcibly reminded him of Southey's poem about the "Cataract of Lodore,' ""for the water," said he, "comes running, and jumping, and dancing, and leaping down in almost every imaginable variety of form and motion." Thereupon. Frank, being invited to recite the poem, gave the following:

THE CASCADES OF ROCKY GLEN.

[The Cataract of Lodore.]

"How does the water come down at Lodore?"
My little boy asked me thus, once on a time;
And moreover he tasked me
To tell him in rhyme.

Anon at the word,

There first came one daughter,
And then came another,

*Fig. 21, the turbine wheel, consists of a fixed
upright cylinder I J, which admits the water, placed
upon another and larger fixed cylinder, represent-
ed here by the inner curves, the latter encompassed
by the moving wheel A B, in the form of a rim.
Through N passes a shaft, by which motion is im-
parted to machinery. From the tall central cylin-
der the water passes, under great pressure, into the
curved compartments of the larger fixed cylinder,
where it receives such a direction as to strike the
divisions of the revolving rim to the best advantage.
B As this wheel acts upon the principle of hydrostatic
pressure, its power is proportionate to the height
of the column of water in the central cylinder I J.
When a column of water can be obtained of consid-
erable height, the turbine wheel is an engine of
great power.
It is extensively used in the cotton
factories of Lowell, Mass.

P

To second and third the request of their brother, And to hear how the water comes down at Lodore, With its rush and its roar,

As many a time
They had seen it before.

So I told them in rhyme,

For of rhymes I had store.

From its sources, which well
In the tarn on the fell;
From its fountains

In the mountains;.

Its rills and its gills;

Through moss and through brake,
It runs and it creeps
For a while, till it sleeps
In its own little lake.
And thence, at departing,
Awakening and starting,
It runs through the reeds,
And away it proceeds,
Through meadow and glade,
In sun and in shade,

And through the wood-shelter,
Among crags in its flurry,
Helter-skelter,

Hurry-skurry.

Here it comes sparkling,
And there it lies darkling:
Now smoking and frothing,
In tumult and wrath in,
Till, in this rapid race
On which it is bent,
It reaches the place
Of its steep descent.
The cataract strong
Then plunges along,
Striking and raging,
As if a war waging
Its caverns and rocks among;
Rising and leaping,
Sinking and creeping,

Swelling and sweeping,
Showering and springing,

Flying and flinging,
Writhing and ringing,

Eddying and whisking,

Turning and twisting,
Spouting and frisking
Around and around,
With endless rebound;
Smiting and fighting,
A sight to delight in ;
Confounding, astounding,