9 



118 ANNUAL OF SCIENTIFIC DISCOVERY. 



run across its center. A straight line is marked in this position, and 

 the instrument is applied again to another part of the circumference, 

 so as to mark in the same manner another line intersecting the first. 

 The point of intersection is of course the center of the wheel. 



New Spring Balance for Time Keepers. The ordinary chronometer 

 or watch-balance, it is well known, plays on points at the ends of its 

 axis, and its motions or vibrations are governed by the tension of a 

 coiled spring, which in watches is called the hair-spring. This 

 balance, which has been called the most beautiful invention in 

 mechanics, has, of late years, to a considerable extent, taken the place 

 of a pendulum in larger time-pieces ; and in such cases the points of 

 the axis of the balance have been made to rest upon friction wheels 

 to reduce their friction. In the present instance, however, the points 

 and the spiral-spring are thrown aside, and a long, straight, thin, and 

 narrow steel spring is made to perform the office of both. The spring 

 is secured to the clock-frame at both ends and strained tight, and the 

 balance itself, consisting, in this instance, simply of a straight bar, 

 loaded with a ball at each end, is suspended at or near the middle of 

 the spring ; the spring passing through the middle of the bar at right 

 angles. The spring is thus made to serve the double purpose of a 

 frictionless suspension for the balance and a governor of its motions. 



The force of torsion, as it is called that is, the force with which 

 a twisted wire or thread of glass tends to untwist itself has been 

 used before in certain instruments for philosophical purposes, as in 

 some magnetic instruments where the magnetic bar is suspended at 

 the lower end of the wire ; and, when used for such purposes in this 

 manner, the force of torsion of the wire has" been measured by removing 

 the magnet, putting a given weight in its place, and counting the 

 number of vibrations it accomplishes in a given time ; and such an 

 arrangement as this has even been applied to a time piece. But in 

 the present arrangement, where the flat spring is secured at both ends, 

 and strained tight, so that the time piece can be moved about like a 

 watch, the governing force of. the balance is -not derived from the 

 simple torsion of the spring, but is also due in part to, and can be 

 varied by, the force with which the spring is strained. The exact 

 adjustments for time are made either by an adjustable slot, through 

 which the spring passes near its end, or by a screw adjustment of the 

 balls, or both. 



Improvement in Turbine Wheels. In this improvement the orifices 

 of discharge from the buckets in the wheel are capable of adjustment 

 for different heads of water without changing the curvature of the 

 buckets. This is effected by attaching to the bucket a sliding plate of 

 the same width and curvature as the bucket ; the moving of this plate 

 outward extends the curvature of the bucket and diminishes the 

 orifice of discharge. 



