R 0 L L I N 
the common hay lands, it is a good mode to proceed up one 
side of the field, and down the other, somewhat in a similar 
manner, as by that means the work may be the most com¬ 
pletely executed, and with the least trouble. 
A writer, in the Communications to the Board of Agri¬ 
culture, mentioned above, has remarked, that sward and 
meadow land should always be rolled in April or the be¬ 
ginning of May, and when the ground is in a moist state, as 
it causes the grass to be of a more kind nature, and reduces 
the hills raised by the ants to a proper state for being mown over. 
Likewise on such new grass-lands as have been just re¬ 
stored to the state of sward, and which are often thin and 
patchy, when seeds are sown over such parts, the roller may 
frequently be run over them in order to force in the seeds; 
but a better practice is to turn sheep upon the lands, con¬ 
fining them upon such patches by means of hurdles, in order 
that they may tread them in. In either case, a rather moist 
time should be chosen for the purpose. In cases of this na¬ 
ture, where there is a degenerate sward, Mr. Amos, in his 
Minutes on Agriculture, advises the use of his compound 
toller, which should be run over the ground early in March, 
when the sward will admit the spikes without being injured 
by the feet of the horses, the land being previously covered 
with well-rotted dung, or compost, in the proportion of 
from about eight or ten tons to the acre. It should be well 
rolled in different directions, till the surface sward is pretty 
much broken, then sowing the grass seed over the land, 
and after letting it be well dressed with the sward dresser, 
and all the rubbish collected cleared away, rolling it well 
■down with the plain roller, and admitting no sort of live¬ 
stock afterwards upon it. In this method of using the roller 
vast improvements may, in many cases of degenerated or 
worn-out grass-lands, be effected, without incurring any 
very heavy expenses, or much trouble. 
ROLLING, in Sea Language, that motion by which a 
ship vibrates from side to side. Rolling is, therefore, a sort 
of revolution about an imaginary axis, passing through the 
centre of gravity of the ship ; so that the nearer the centre 
of gravity is to the keel, the more violent will be the roll; 
because the centre about which the vibrations are made is 
placed so low in the bottom, that the resistance made by the 
keel to the volume of water which it displaces in rolling, 
•bears very little proportion to the force of the vibration above 
the centre of gravity, the radius of which extends as high as 
the mast-heads. But if the centre of gravity is placed higher 
above the keel, the radius of the vibration will not only be 
diminished, but such an additional force to oppose the motion 
of rolling will be communicated to that part of the ship’s 
bottom as may contribute to diminish this movement con¬ 
siderably. 
It may be observed, that, with respect to the formation of 
a ship’s body, that shape which approaches nearest to a circle 
is the most liable to roll; as it is evident, that if this be 
agitated in the water, it will have nothing to restrain it; 
because the rolling or rotation about its centre displaces no 
more water than when it remains upright; and hence it be¬ 
comes necessary to increase the depth of the hold, the rising 
of the floors, and dead or rising-wood afore and abaft. 
ROLLING FORK, a river of Kentucky, which runs 
•into the Ohio. Lat. 37. 47. N. long 86. 18. W. 
ROLLING-MILL, in metallurgy, and particularly in the 
iron manufacture, is a mill for reducing masses of iron or 
other metals into even parallel bars, or flat thin plates: this is 
'effected by passing the metal, whilst red-hot, between two 
cylindrical rollers of iron or steel, which are put in motion by 
the power of the mill ; and being so mounted in a strong 
metal frame, that they cannot recede from each other, they 
•compress the metal which is passed between them, and 
reduce it to a thickness equal to the space between their 
surfaces. 
It Requires a'most enormous power to put in motion the 
^rollers which are employed for laminating iron in the large 
way; and for this reason, the greatest number of rolling- 
mills are situated upon the banks of rivers which have the 
advantage of a sufficient fall to turn the machinery. Of late 
Vol. XXII. No. 1494. 
G - M I L L. 197 
years, the superior power of steam-engines has been adapted to 
rolling-mills, as the waste heat of the furnaces used for heating 
the metal may be employed, in part, to raise steam for the 
engines which turn the roller. 
Rolling-mills were not very generally used in the iron 
manufacture till within these sixty years. The old mills 
which were first used are extremely simple; two separate 
water-wheels are placed on the opposite sides of the mill, 
with their axles in the same direction, but at different heights, 
so that one wheel can be connected with the upper, and the 
other with the lower roller: it therefore requires the two 
wheels to have the water delivered at opposite sides, to make 
them revolve in different directions, in order that the upper 
surface of the lower roller, and the under surface of the 
upper roller, may move in the same direction, and pass the 
iron between them. The construction of the rollers generally 
used in such mills is shewn at figs. 1, 2, and 3, of annexed 
plate, except that the two rollers, F and G, are there 
shewn with equal pintons, d and e, fixed upon the ends of 
their pivots, to compel the two to revolve equally together; 
whereas, in the mills with two separate wheels, no provision 
is made to ensure the equal motion of the two. The gud¬ 
geons, or necks, of the lower roller, G, are supported in 
brasses, fitted into strong carriages of iron E, E, which 
have holes through their ends, to receive four strong iron 
bolts, A A, BB; these stand perpendicular, and form the 
frame, to retain the rollers at the proper distance, being 
fitted through the carriages E with heads below, so that 
they cannot draw out The upper ends of the bolts are cut 
with screws, upon which nuts, a, a, are fitted ; and these 
being turned round by iron handles or wrenches, screw down 
the pieces D, D, and advance the rollers nearer together; or, 
by a contrary motion, increase the distance between them : 
i (fig. 3) is a strong iron bar, extended from one bolt, A, to 
the other, B, and fixed fast; it supports an iron plate, 
forming a kind of table before the rollers, to guide the iron 
through them. The rollers have square heads upon the ends 
of their gudgeons; and upon these squares, large cast-iron 
sockets or boxes, as L, are fitted, and these, at the other 
ends, are fitted upon similar squares on the ends of the 
water-wheel axis. A little play or looseness is admitted 
in all these squares, because the upper roller is set at dif¬ 
ferent heights, according to the thickness of the work 
which is to be rolled between them : this play is required to 
allow the rollers to move freely, when they are not exactly in 
the line of the water-wheel axis: it is to accommodate this 
circumstance that the principal care is required in con¬ 
structing a rolling-mill. Our readers will gain a good idea 
of the best proportions of a mill with two independent water¬ 
wheels, from thefollo wing directions for building one inNorth- 
umberland, which were given by Mr. Smeaton upwards of 
forty years ago. The two water-wheels are to be under-shot, 
and of different sizes, viz.: 15ft. 4 in., and 14 ft. 8in., the 
mean diameter being 15 ft. The breadths in their float- 
boards are to be three feet each, the small wheel being laid 
lower than the other by seven inches: this, with the differ¬ 
ences of their diameters, will make the centre of the large 
wheel eleven inches higher than the other. The different 
heights of the crowns of the falls or breasts, down which 
the water descends to act upon the wheels, and the positions 
of the water-shuttles, are to be so adjusted, that the gates or 
shuttles being equally drawn up by their starts, the wheels 
will, as near as possible, revolve in equal times, and with 
equal power. The rings of the water-wheels are to be made 
of cast iron, that their weight may act as flies: the ring of 
the lesser wheel is to be made six inches in thickness by- 
six inches deep, while that of the larger is to be only five 
by six. The greater quantity of matter in the lesser wheel, 
therefore, will give it nearly the same momentum as the 
larger wheel. 
The rings of the water-wheels are each to be formed by 
eight pieces or fellies, the exterior circle of the greater wheel 
being thirteen feet diameter, and that of the less twelve feet 
four inches: the length of the fellies is to be about half an 
inch shorter than their true length, jn order to admit an oak 
3 E ,wedge 
