ON THE DISTINCTION OF VARIETIES OF PLANTS. 103 
from above (overshot). A metal wheel is fastened to the exterior rim 
of the water-wheel, in which the cogs are two inches apart, and b} r 
which a pinion wheel, three feet in diameter, and having forty-cogs, 
is worked. 
On the other end of the axle of this pinion, which may he of any 
required length, and which in this case is in the interior of the build¬ 
ing, a mitre wheel, of the same diameter of the pinion, viz.—three 
feet, is attached, and this works a small wheel of sixteen inches 
diameter, with thirty two cogs, which is staked or fastened on the 
axle that supports the two drums. 
The drums are each four feet in diameter, and a leathern strap of 
three inches in width, works over them, and over a block or chieve, 
which is attached to the end of the axle on which the circular-saw is 
staked; a block of one foot in diameter and three inches broad, works 
a saw three feet in diameter. Two circular saws are worked bv each 
•/ 
of these two drums, and the quantity of stuff they are capable of 
cutting is quite astonishing. An idea of their power will be given, 
by stating that we had a cut run through the whole centre of a larch 
tree, thirty feet in length, and six inches in diameter, at the ground, 
in the short space of one minute and twenty seconds. 
Mr. Ward, the intelligent forester at Glenmore Castle, informed 
us, that he has had thirty three perches of twenty one feet pailing, 
for folding sheep, made by six men in a single day. 
Mr. Dee (Vol. 3, p. 488) is therefore, perfectly correct, when he 
states that the value of a circular saw in economising labour in the 
farm-yard would be very great indeed. 
Small circular saws are frequently worked in the manner that lathes 
are, by a strap or rope round a wheel, motion being communicated 
either by the foot, or by an additional man, but such do not possess 
much power; the better way is to drive the saw by means of a drum 
attached to some quickly revolving axle of a corn-mill, steam-engine, 
or thrashing machine. 
NATURAL HISTORY. 
Article VIII.—ON THE DISTINCTION OF VARIETIES OF PLANTS, 
BY MR. F. F. ASHFORD. 
The collecting of varieties under their proper species is a work no 
less necessary than that of collecting the several species under their 
proper genus. Such differences as are only incidental to vegetables, 
and are not found constant and unchangeable in them, are to be 
