Science Siftings

New Zealand Tablet, 14 July 1910, Page 1115

Science Siftings

BY ‘VOLT’

Steel Mail Cars.

The United States postal department is having all of the mail cars on the railroads throughout the country v-ij- . s^ The reason for this new method of car building is to protect the mail and the clerks in train wrecks or in other accidents where cars are liable to come together and eventually take fire. The cars are built entirely of steel, no woodwork being used at all. From the steps on the ends of the cars to the framework holding the large mail bags inside, everything is of the best quality of steel. J

The Use of the Potato.

Weight for weight, bread is six times more nourishing than potatoes. The potato thrives best in Portugal, where the average yield is twelve tons to the acre. The potato is three-quarters water, and is deficient in nitrogen besides. Hence it is not in itself a perfect food. But eaten with meat the combination is ideally perfect. The gum on the back of postage stamps is made of farina extracted from potatoes. The Dutch make a molasses-like syrup of potatoes, and potatoes form the starch that stiffens the world’s shirts and petticoats. A very powerful brandy is made of x.L P j* ato ' The potato but too often adulterates cocoa, potted meats, honey, butter, and tapioca. Potato spirit, a very pure alcohol, is used to fortify wines, and it is prophesied that this spirit will supplant gasoline as the motive power of automobiles. From potato leaves cigarettes are made, and from potato pulp buttons, combs, and penholders.

Suspension Bridges. Suspension bridges, some of them of considerable length, were common in Peru in the days of Incas. They were formed of cables of twisted oziers passed over wooden supports and stretched from bank to bank, then bound together with smaller ropes and covered with bamboos. The road from Cuzco to Quito is still noted for frail bridges of this sort, which are in constant use and span deep chasms. The Chinese also, according to Kircher, have for centuries been familiar with the suspension theory, and have constructed chain bridges in which the weight of the roadway is supported by the tension of the chains. The first iron suspension bridge in Europe was built over the Tees, near Middleton, in 1741, for the use of miners. Two chains were stretched in a straight line, steadied by ties from the banks below, and the roadway for foot passengers was supported to the chains. The modern suspension sysi nn* Poetically dates from 1816,- when bridges, both over 100 feet in length, were successfully completed at Galashiels and Peebles.

Importance of Carbon. The electric arc light as now so commonly used is produced by the passage of a powerful electric current between the slightly separated ends of a pair of carbon rods, or carbons, about 12 inches long and from three-eighths to one-half inch in diameter, placed vertically end to end in the lamp. The lamp mechanism is so constructed that when no current is passing the upper carbon, which is always made the positive one, rests upon the lower by the action of gravity, but as soon as the electric current is established the carbons are automatically separated about an eighth of an inch, thus forming a gap of high resistance in the electric circuit, across which the current is forced, resulting in the production of intense heat. The ends of the carbons are quickly heated to brilliant incandescence, and by the burning action of the air are maintained in the form of blunt points: As the carbons burn away the lamp mechanism feeds the upper one downward just fast enough to maintain the proper separation. The carbons are not heated equally, the upper or positive one being much the hotter. A small cup-shaped cavity or ‘ crater,’ ordinarily less than an eighth of an inch in diameter, is formed in its end, the glowing concave surface of which emits the greater part of the total light. In lights of the usual size something like half a horse-power of energy is concentrated in this little crater, and its temperature is limited only by the vaporisation of the carbon. Carbon being the most refractory substance known, the temperature of the crater is the highest yet produced artificially, and ranks next to that of the sun. It is fortunate that nature has provided us with such a substance as carbon.