oints
which it is essential should be distinctly understood, in order to
comprehend the relative merits of the boilers used in travelling
steam-engines.

The motion which is primarily produced in a steam engine is a
reciprocating or alternate motion of the piston from end to end of the
cylinder; but the motion which is necessary to be produced for the
purposes to which the engine is applied, is rarely or never of this
nature. This primary motion, therefore, is almost always modified by
some machinery interposed between the piston and the object to be
moved. The motion most generally required is one of rotation, and this
is accomplished by connecting the extremity of the piston-rod with a
contrivance constructed on the revolving axle, called a _crank_. This
contrivance does not differ in principle from the common winch, or
from the key which winds a clock. The motion of the piston-rod
backwards and forwards turns such a winch. At each termination of the
stroke, the piston, from the peculiar position of the crank, loses all
power over it. To remedy this two cylinders and pistons are generally
used, which act upon two cranks placed on the axle at right angles to
each other; so that at the moment when one of the pistons is at the
extremity of its stroke, and loses its power upon one crank, the other
piston is at the middle of its stroke, and in full operation on the
other crank. By these means an unremitting force is kept in action.

_Edinburgh Review._

* * * * *

SONG.

BY ROBERT GILFILLAN, AUTHOR OF "ORIGINAL SONGS."

Tune.--"_Gin a body meet a body._"

Bonnie lassie, fairest lassie,
Dear art thou to me;
Let me think, my bonnie lassie,
I am lov'd by thee!

I speak na of thy ringlets bright,
Nor of thy witching 'ee;
But this I'll tell thy bonnie sel',
That dear art thou to me!

O! beauty it is rare, lassie,
And beauty it is thine,
Yet my love is no for beauty's sake,
'Tis just I wish thee mine!

Thy smile might match an angel's smile,
Gif such, save thee, there be;
Yet though thy charms my bosom warms,
I'll tell na them to thee!

Thy sunny face has nature's grace,
Thy form is winsome fair;
But when for long thou'st heard that sang,
O! wherefore hear it mair?

Thy voice, soft as the hymn of morn,
Or evening's melodie,
May still excel, as a' can tell,
Then wherefore hear't frae me?

Bonnie