DYNAMOMETER. An instrument for measuring power of any kind, as the strength of men and animals, the force of machinery, the magnifying power of a te lescope, &c. An instrument for measur ing animal force was invented by Mr. Graham many years ago, and afterwards improved by Desaguliers ; but as it con sisted of wooden works, it was too heavy and bulky to be conveniently used for ordinary purposes. Leroy, of the Aca demy of Sciences of Paris, proposed a dynamometer, which consisted merely of a tube of metal of ten or twelve inches in length, placed vertically on a stand, and containing a spring in its interior, which indicated by its compression the amount of the force applied. The instrument was in fact the same in principle as the common spring balance.
The most convenient dynamometer is that of Regnier, which is described in the Journal de l'Ecole Polytechnizue. It con sists of an elliptical steel sprang of about 12 inches in circumference, and the force is applied either by pressing the two ver tices of the axis minor against each other, or by drawing in opposite directions the two ends of the axis major. In both
cases the sides of the spring are made to approach each other ; and thus they move an index which marks the degree of approximation on a semicircular scale. By means of this machine the mean force is ascertained which a man can exert with the right hand, or with the left, or with both together, and in various positions of his body. Some results re lating to the average strength of men at different ages, and of different weights and sizes, have been deduced by M. Quetelet of Brussels, from numerous ex periments with his dynamometer. In testing the value of ploughs, the dynam ometer should be used, instead of plough ing a given space of land.