Robert Hooke und die frühe Geschichte der Federwaage

A large number of the so-called electronic balances, for example those using wire strain gauges, are based on the elastic deformation of solid materials, and on the electrical measurement of the resulting changes in length. Such instruments must therefore be grouped into the class of spring balances. The spring balance operates within the limits of proportionality according to the law discovered by and named after Robert Hooke. No precise information about the spring balance can be found so far in the literature about balances: it is assumed that it was invented before 1700, without knowledge of the name of the inventor. As the result of a literature research it is shown that Robert Hooke found experimentally in 1676 with „ut tensio sic vis”︁ not only the physical principles which led to the law of elasticity: he also drew practical conclusions from it, and in the treatise De potentia restitutiva, published 1678, he described the most important types of spring balances. Experiments carried out by him to demonstrate the reduction of gravity with increasing altitude by using such a balance led, however, to a negative result because of its lack of sensitivity. Further developments for more than 100 years were necessary, until the spring balance come into more general application.     

Über die Aufhänge- und Anzeigevorrichtung der ägyptischen Waage der Pharaonenzeit

A number of different and partly contradictory interpretations about the suspension and the indicator system of the ancient Egyptian balance has been given so far. In this article previous explanations of these devices are presented and critically considered; at the same time the balance of the Egyptians is included in the complete evolution of this instrument. Based on original Egyptian colour drawings on papyrus taken from the Book of the Death and considering weighing techniques, it is stated that all interpretations given so far are not capable of providing a satisfactory explanation of the function of these devices. The interpretation given already in 1888 by Sir Flinders Petrie comes closest to the real function of the indicator system: According to his assumption the device consisted of a solid pointer attached to the beam, in relation to which a plumbline was observed after the oscillations had stopped. This interpretation, however, has to be varied or to be complemented by taking into consideration the special drawing technique of the ancient Egyptians: Processes were drawn in a reproduction technique which consisted in the simultaneous combination of a top view and a side view. A new hypotheses about the function of the suspension and the indicator system of the ancient Egyptian balance is presented, which has the advantage of agreeing completely with the Egyptian drawing technique and which, in addition, ensures optimum precision of the weighing procedure.