Man has not been able to tell definitely just what the greatest depth of the ocean is, because it would be a practically unending task to go over every bit of it to take measurements. A great many exploring expeditions have been sent out to determine that interesting information so far as possible, however, and one of these, the Murray-Challenger expedition, has reported that the greatest depth that could be found in the Atlantic Ocean is 27,366 feet, in the Pacific Ocean 30,000 feet, in the Indian Ocean 18,582 feet, in the Southern Ocean 25,200 feet and in the Arctic Ocean 9,000 feet. They also stated that the Atlantic Ocean has an area in square miles, of 24,536,000; the Pacific Ocean, 50,309,000; the Indian Ocean, 17,084,000; the Southern Ocean, 30,592,000 and the Arctic Ocean, 4,781,000. Why do We Say “Get the Sack”? The use of the expression “get the sack,” when we mean “to be discharged,” originated through the impression made upon people in this country when stories were brought to them of the way the Sultan of Turkey disposed of members of his harem of whom he had tired. When he wanted to get rid of one of his harem he was said to have had her put into a sack and thrown into the Bosporus. People who heard of this report repeated it to others and they became so used to telling the tale that they slipped quite naturally into the habit of saying “to get the sack” when they meant that they expected to be put out of a position suddenly. In very much the same way the phrase “Hobson’s choice” is supposed to have resulted from the story told here of a livery-stable keeper at Cambridge, England, called Hobson, who obliged each customer to take the horse nearest the stable door, when a wish to hire one was expressed, even though he might permit customers to make the rounds of all the stalls, examining and perhaps selecting other horses. Since the interest inspired by that report, “Hobson’s choice” has come to mean a choice without any alternative, or the chance to take the thing which is offered or nothing. Why do We Call Them X-Rays? At the time the discovery of X-rays was announced by Prof. Wilhelm Conrad Röntgen of the University of Würzburg, Germany, he was not sure of their exact nature, and so he named them “X-Rays,” because “X” has always been understood to be the symbol for an “unknown quantity.” They are invisible rays transmitted through the air in a manner similar to light. They are produced by passing unidirectional electric current of from twenty to one hundred thousand volts pressure through a specially constructed high vacuum tube, within which rays radiating from the surface of a concave cathode (the negative electrode of a galvanic battery), are focused upon and bombard a target of refractory material such as tungsten, iridium, platinum, from which focus spot the X-rays radiate in all directions.