Democratic Sentinel, Volume 8, Number 41, Rensselaer, Jasper County, 7 November 1884 — A HAIR’S THICKNESS. [ARTICLE]

A HAIR’S THICKNESS.

A Delicate Machine in the Post office Department and Its Use. A curious little machine in the office of the chief of the stamp bureau of the I’ostoffice Department is the cause of the cancellation of the contract of the New England firm with the Government for furnishing envelopes to the Postoffice Department* It is a queerlooking contrivance—a cross between a set of butchers’ scales and ordinary grocer’s scales, or, rather, a combination of the two. There is a larger dial, like the face of a clock, with the little hand that flies around the face pointing to the figures at the side, which are arranged like the figures on the clock face, with little dots between. “You see three dots?” said the gentleman in charge, inquiringly. “Well, the space between these indicates one-sixteen-thousandth of an inch. Getting it down pretty fine, isn’t it? Yon see this movable piece of iron here, which comes down with a smooth surface upon this other solid surface? Well, the raising or lowering of that moves the pointer which runs round the dial. To test the thickness of a sheet of paper, we simply place it between this movable piece and the solid surface below, and when the movable piece of iron comes down upon the paper, the hand registers the true thickness of the paper. Delicate instrument? Well, I should think so. Just give me a hair from your head, will you?” Then he took a hair and slipped it deftly between the movable pieces. The hand on the dial followed the motions of the screw until it stopped at the figures 20. Just 20 10-lOOOths of an inch in diameter,” he Baid. “Now let mo try a hair from your mustache. They are generally much larger, especially if you have been in the habit of shaving.” He took up a pair of scissors and clipped off a hair from the mustache and placed it iri position. The hand stopped at 50. “Fifty 16lOOOths of an inch thick,” he said. “That shows thq effect of Bhaving. I measured a hair from the hand of a gentleman a few minutes ago which was 10 16-lOOOths thick, hut those in his mustache were precisely the same thickuoss, the reason being that he had never shaved. Yes, that is the machine that proved that the firm making our envelopes was not fulfilling its contract,” he said, as he foil back admiringly. _ . “Bv this dial wo can sqp just the thickness. By this lever, which is very much like a pair of grocer’s soales, we can tell just what pressure the paper will stand. You see, we have two other movable pieces of iron lifer#, with a holo entirely through both, and a plunger which passes through that hole. Well, we put the paper between those pieces, which, when they arb pressed together by this lever, hold ‘lit firmly. The plunger, which pasiefc through the opening in the two pieces of iron, encounters this paper tluui firmly held. To know what the pressure is, we have the plunger attached to a scale lever with a weight attaoMfi like an ordinary pair of scales, and, by moving this weight out along the lijver until the paper breaks, of course we cgn see just what the weight is tbit made it break. See! Very simple ftfwr you understand it. Well, that is wfckt the paper-makers thought after tfyfeT had lost an SBO,OOO contract by it. It woe a new thing to them, but they, acknowledged that they were beaten when they saw it. ” This delicate instrument, only itmcently invented, is a companion pifQe .to the Beales in the Assayer’s office pf the Treasury, by which the weight of hair is accurately tested. —Washing ton Post.