Enquire within upon everything by Robert Kemp Philp

976. _Why docs the Hand of the Weather Dial change its Position when the

Column of Mercury rises or falls?_ Because a weight which floats upon the open surface of the mercury is attached to a string, having a nearly equal weight at the other extremity; the string is laid over a revolving pivot, to which the hand is fixed, and the friction of the string turns the hand as the mercury rises or falls.