Show minute measure measurements 7 ants because the balance wheels ot of watches expand and contract with changes of temperature they run slower and taster faster according to cir cun stances by making them of dit dif erent ferent kinds of metal having different degrees of expansion with increase of temperature the eff effect act of their changes on the running of watches may be almost entirely eliminated but in dealing with such a problem it Is necessary to know the expansibility of the metal employed A means of measuring it Is fur dished by an instrument called a in which a system of dell 1 I levers or a chain of gear wheels irr fifles the motion of a pointer over a graduated scale hundreds of time at a meeting of the physical society in london not long ago a vas exhibited which bad had a magnifica tion of 1 times so that the change in the length of a piece of steel caused by a single degree of rise or tall fall of temperature nas vas clearly measured by it |