The hands of this very mysterious timepiece carry their own motive power, and consist of unequally balanced levers, so to speak, in which the clockwork arrangement is intended to disturb the equilibrium. This property is employed to indicate the hour and the minute, as we will attempt to show.
The minute hand is the balance, and it is very exactly poised. In the round box fitted to the end of this hand a plate of platinum is displaced by clockwork. The centre of gravity being displaced every instant by the revolution of the weight which goes round once in an hour, the minute hand is forced to follow, and carries the hour hand with it. By the hidden arrangements the hands are dependent one upon the other, but remain independent in movement. If they be moved backwards or forwards they will return automatically to their respective places, and if turned quickly round the minute hand will return to the proper minute, and the hour hand to the hour.
The mechanism is simple and ingenious; the principle, however, is not absolutely novel, and before M. Robert applied it many attempts had been made to move indicators by the machinery they themselves contained. But M. Robert has succeeded in adapting the idea beneficially and usefully, giving it a practical as well as an elegant shape.
A New Calculating Dial.
Fig. 882.—A new calculating dial.
Fig. 883.—Reverse view.
The small instrument herewith illustrated (figs. 882 and 883) is very serviceable for calculators, and its size adapts it for the waistcoat pocket. It can be used to calculate by addition, subtraction, multiplication, and division. Logarithms can be found, and the powers and roots of numbers—even trigonometrical calculations may be made by its aid. We need not go into any details regarding the principle of the little “circle.” Such explanations are only wearying and unsatisfactory at best. The principle is, simply stated, the theorem that the logarithm of the product of two numbers is equal to the sum of their logs. The size of the dial will of course regulate the length of the calculation. The instrument depicted permits of calculation to three figures with exactitude. M. Boucher, the inventor, hopes to succeed in perfecting an instrument of small size which will combine all desiderata, and calculate to high powers.
The Pedometer.