Indeed, for a definition of that limitless subject which includes all the phenomena that stand the warp and stress of change, one might adapt a famous epitaph - si historiam requiris, circumspice.
It has been suggested 2 that an iron rod under magnetization may be in the same condition as if under a mechanically applied longitudinal stress tending to shorten the iron.
In the latter case the first application of stress is always attended by an increase-often a very great one-of the magnetization, whether the field is weak or strong, but after a load has been put on and taken off several times the changes of magnetization become cyclic. From experiments of both classes it appears that for a given field there is a certain value of the load for which the magnetization is a maximum, the maximum occuring at a smaller load the stronger the field.
On the other hand, a study of the plant-life of past ages tends to the conviction that too much stress may be laid on the imperfection of the geological record as a factor in the interpretation of palaeontological data.
In considering the motion of a fluid we shall suppose it non-viscous, so that whatever the state of motion the stress across any section is normal, and the principle of the normality and thence of the equality of fluid pressure can be employed, as in hydrostatics.
He puts far greater stress than his predecessors upon the sympathetic pleasures, and thus quite avoids that appearance of mean prudential selfishness that is such a depressing feature in Paley and Bentham.
Perrier, at first laying greater stress on the nature of the pedicellariae and afterwards on the form of the mouth-skeleton, has gradually perfected a scheme of five orders: (I) Forcipulata, with pedicellariae stalked, and straight or crossed; (2) Spinulosa, with pedicellariae sessile and forcipiform; (3) Velata, with membraniferous spines; (4) Paxillosa, pedicellariae represented by an ossicle of the test and the spines covering it, the whole forming a paxilla; (5) Valvata or Granulosa, with pedicellariae sessile and valvular or salt-cellar shaped.
As a simple example, take the case of a light frame, whose bars form the slides of a rhombus ABCD with the diagonal BD, suspended from A and carrying a weight W at C; and let it be required to find the stress in BD.
He lays stress on the relation of the supposed confession of faith of Constantine, embodied in the forgery, to that issued by the emperor Constantine V., pointing out the efforts made by the Byzantines between 756 and the synod of Gentilly in 767 to detach Pippin from the cause of Rome and the holy images.
Let a frame (without redundant members), and the external forces which keep it in equilibrium, be represented by a diagram constituting one of these two plane figures, then the lines in the other plane figure or the reciprocal will represent in direction and magnitude the forces between the joints of the frame, and, consequently, the stress on each member, as will now be explained.