FLYING SQUIRREL, Piero-rays, the name given to a considerable number of species of the squirrel family (seturidrs), which have a fold of the skin of the flanks extended between the fore and bind legs, and partly supported by bony processes of the feet, by means of which they are enabled to take extraordinary leaps, gliding for a great distance through the air. The tail also aids to support them in the air, as well as to direct their motion, its hairs extending laterally " in a sort of feathery expansion." The dentition is similar to that of true squirrels, with which also the habits generally correspond. One species (P. siWricus) is found in the n: of Europe and of Asia; several species are natives of North America, and others inhabit the s.e. of Asia and the Indian archipelago. The European species is about the size of a rat, grayish-ash color above, white below, the tail only half the length of the body; it lives solitarily in the forests. Its fur is of little value, but skins are sometimes mixed with those of the gray squirrel, to impose on the purchaser. The most common North American species (P. volucella), abundant from the gulf of Mexico to Upper Canada, is fully 5 in. long, with a tail of 5 in. addi tional, fur included. It is of a brownish-gray color above, white beneath; a black line surrounds the orbit of each eye. All the species inhabit woods, and the night is their time of activity. They feed not only on nuts and young shoots of trees, but also on small birds. They are extremely easy of domestication.
In gliding from tree to tree, the common American F. S. descends obliquely and with very rapid motion, until near the tree which it seeks to reach, when it wh.!els Inwards.
and alights at about a third of the height which it was from the ground on the tree which it left, the distance between the trees being perhaps 50 feet.
is the name given to a compound of metallic arsenic and arseniom acid, obtained by the partial oxidation of the metal, on exposure to air, and which is sold on the continent for the purpose of killing flies.
See Eiroximt.
a large heavy wheel applied to a steam-engine or other machinery in order to equalize the effect of the moving power. Its action depends upon the principle, that a body once set in motion retains a certain amount of moving force or momentum.
This increases with the weight of the body and the velocity of its motion, and may be expressed relatively by multiplying the weight by the velocity; or stated otherwise, the force required to destroy the motion of a body is equal to that which set it in motion. Thus, a heavy wheel becomes a sort of reservoir of force, when set in motion.
The are two principal cases in which the fly-wheel is commonly applied: first, when the motive power is intermittent or irregular; and second, when the resistance or work to be done is intermittent or irregular. The crank is a good example of the first case. If the force be applied only downwards, as in the common foot-lathe, it will be intermittent, and the crank must rise independently of the prime mover. This is effected by applying a fly wheel, which is set in motion by the descending 'pressure of the foot acting upon it through the crank; and the momentum it has thus acquired lifts the crank again to the point where it can be acted upon by the foot. It also carries the crank over the dead points (see CRANK), where even a double action of pulling and pressing would be inef fective. The case of a steam-engine turning a long shaft which passes through several workshops, and by means of bands drives a number of lathes, punching, drilling, plan ing machines, etc., is a common example of the second case, the resistance or work to be done being very variable from one moment to another. in such work as that of a punching-machine, the engine need not be nearly of sufficient power to directly force the punch through the metal, and yet by the aid of the fly-wheel it may do it; for while the punch is rising, the engine is momentum to the flywheel; and when the descending punch meets with the resistance it has to overcome, this reserved momen tum is added to the direct power of the engine, the punch is forced through, and the speed of the fly-wheel slackened, in proportion to the resistance.
The principle of the fly-Wheel is sometimes applied in other forms than that of a wheel, as in the hand-coining press, where a heavy ball is fixed at each end of a long lever, which is made to swing round with considerable velocity, and the accumulated momentum is concentrated upon the blow.
FO. See BUDDIIA.