If the knives are kept properly adjusted and the mower is not abused by trying to cut wires, stones, or by being stored where it becomes rusty, it will seldom need sharpening.
Keep all bolts tight.
246. Storing Mowers. When storing for the winter, grease the knives with a heavy coat of unsalted lard, or cover them with some other protective material.
247. Scissors and Shears. In popular language, there is no distinction made between scissors and shears. Technically defined, scissors are less than six inches in length. Any similar cutting device of greater length is called shears. Both are devices used for cutting cloth, paper, pruning trees, and many other purposes. They consist of two knives riveted together at some point between the handle and the point of the blade. The two blades are so adjusted that as the open scissors are closed, they touch lightly as they pass each other until the tip is reached. When the scissors are closed, the blades should touch only at rivet and tip. Scissors not so adjusted will not cut well, even the the blades are very sharp. Dropping scissors often bends the blades. Blades may be straightened as well as sharpened, and thus make good metal scissors like new.
248. Principles Upon Which Incubator Works. A device for hatching chickens is called an incubator. In order to hatch chickens, the incubator must keep an average temperature of 102-1/2 degrees Fahrenheit. The thermometer should be placed in the center of the tray and on a level with the top of the eggs. The temperature of 102-1/2 degrees Fahrenheit must not vary greatly during the incubation of eggs.
The incubator must also permit of suitable ventilation and control of the moisture in the eggs.
There are incubators heated with hot water and others with hot air. The air or water in those commonly used in homes is heated with a kerosene lamp.
The device consists of a heating unit, a regulator or thermostat which, acting upon a valve or damper, regulates the admission of heat into the insulated box containing the trays of eggs, ventilators and a thermometer (Fig. 140).