Rensselaer Union, Volume 11, Number 11, Rensselaer, Jasper County, 28 November 1878 — AMERICAN DISPLAY AT THE PARIS EXPOSITION. [ARTICLE]

AMERICAN DISPLAY AT THE PARIS EXPOSITION.

Wonders of tbe neehanlwl Depart* ment. [From the London Times, Aug. 23.] * * * Perhaps, however, the most Important display In this department, all things considered, is that of the Waltham Watch Company, their first in the European exhibitions. Tne readers of the Times' reports of the Philadelphia Exhibition will not need to be inlormed of- the admirable machinery by which the works of the Waltham watches are produced, or thslr singular exactitude, which enables any part of a watch to be replaced by the corresponding piece of any other watch of the same gride. Iu this mechanical production of machines, America has long led the world, and the mechanism by which the English army rifle Is still produced Is with Immaterial modifications a contribution from the American armories. But in the Waltham works science has been brought to the aid of native Ingenuity to such a degree that eveu since the Philadelphia Exhibition the fabrication of watches has gone 'through a large arc of another revolution. JVhat was beguu by applying such machines that their wo,k was beyond competition on anything like equal terms from any hand work is confirmed by the construction of the most essential parts of a watch on a new principle, which permits an approtch to perfection unattainable by the old mechanism, however produced. Every one knows that the great aHHcutiy lit making chronometers has been the compensation for the effects of expansion and contraction due to change of temperature; but what is less well known is that this difficulty is due less to the balauce, which, by Its construction with a bi-seginental rim (of brass uud steel), may be peifectly corrected, than to the expansion of the balance or hairspring, which, being immensely longer, causes live times the error caused by the expansion or contraction balance-wheel alone. The two pieces must be considered as one, and the compensation effected in the wheel or llm must answer for the spring as well as for itself. The theoretical and insuperable difficulty In this compensation has always been that the error caused by the expansion and contraction of the spring was in a different ratio from that of the correcting expansion or contraction wheel, and the two quantities may be compared to curves with two radii, which could be brought together at two points, but not to coincide throughout, (o that if the compensation at the extremes of temperature is correct, the mean must be in error and vi<r the old compensation was, speaking broa4 ly, in brazing a band of brass on one of steel, a process both theoretically and mechanically eironeous, since the contraction and expansion cau only go on with a certain tendency to disrupture of the elements and consequent inequality of the action. The new balance proceeds on an entirely different arrangement of ihe compensating metals. The rim, of plain steel. Is cut nearly through at the fixed extremities of the semi-circles by several saw-tooth shaped notches, the number determined by experiment, and the brass Is forced iuto these notches. Tbe compensating weights are then put on at the other extremities of the semi-circles instead of being distributed along them empirically, and it Is found possible In this arrangement so to distribute the compensation and compensating weights as to give at will a compensation for

the. mean temperature, either In excess of, or l<ss than the extremes, and of course, to give a compensation which shall coincide throughout, which makes it theoretically possible to give absolute compensation for all temperatures at once. It la difficult to make this clear, without diagrams showing the exact curves attained by experiment; but the nature of the result will be appreciated by those who know the mechanism of the balance. It is simply the theoretical elimination of all error from the compensated balance so far as temperature is concerned. Practically and mechanically there will always be some, due to the inherent lmoerfectlon of human workmanship; but it Is believed that the mean error, and equally the manual adjustment required will be reduced to one-third otfhat actually obtaining under the old form of balance. But to Illustrate how involved are the various improvements in mechanism it may be noted that the delicacy of construction of the new balance would only have been possible with the mechanism Introduced by theWaHbam Company, the precision of which may be judged from that of the micrometer last produced and shown at Paris, which measures the twenty-five-thousandth part of an inch, and even Indicates that so largely that It might be divided under a lens readily Into hundred thousandths. A micrometer screw gauge detects inequalities In > the thread of a screw up to hundred thousandths, and a screw made for the Government Scientific fJommißatoß ■to correct-the measures‘has been constructed in which the maximum of error In the thread la leas than one ten-thousandth part of «u> Inch.