Few will be inclined to dispute the verdict of Forbes: - "His scientific glory is different in kind from that of Young and Fresnel; but the discoverer of the law of polarization of biaxial crystals, of optical mineralogy, and of double refraction by compression, will always occupy a foremost rank in the intellectual history of the age."
60 represents such an embryo under slight compression as seen by transmitted light.
Nearly related is the extinct family Lophiodontidae (inclusive of the American Helaletidae), in which both the upper and lower first premolar may be absent, while the upper molars present a more rhinoceros-like form, owing to the lateral compression and consequent lengthening of the outer columns, of which the hinder is bent somewhat inwards and is more or less concave externally, thus forming a more complete outer wall.
From his views on centrifugal force he deduced the oblate figure of the earth, estimating its compression, however, at little more than one-half its actual amount.
Removing the air or other gas from a vessel, whilst a compression pump compresses the air.
In the Greek school at Alexandria, which flourished under the auspices of the Ptolemies, the first attempts were made at the construction of hydraulic machinery, and about 120 B.C. the fountain of compression, the siphon, and the forcing-pump were invented by Ctesibius and Hero.
The brine is cooled in a tank filled with spiral pipes, in which anhydrous ammonia, previously liquefied by compression, is vaporized in vacuo at the atmospheric temperature by the sensible heat of the returncurrent of brine, whose temperature has been slightly raised in its passage through the circulating tubes.
The opposite axes are connected with springs which are kept in compression by tension of the rope in drawing but come into action when the pull is released, the side axes then biting into wooden guides or gripping those of steel bars or ropes.
The fact that a solid body in its natural state is capable both of compression and of dilatation indicates that the molecules of the body must not be supposed to be fixed rigidly in position relative to one another; the further fact that a motion of either compression or of dilatation is opposed by forces which are brought into play in the interior of the solid suggests that the position of rest is one in which the molecules are in stable equilibrium under their mutual forces.
If one end is sharply pressed in, a compression can be seen running along the spring.
Or we may take it as representing the pressure - excess over the normal pressure in compression, defect from it in extension.
- The velocity with which waves of longitudinal disturbance travel in air or in any other fluid can be calculated from the resistance to compression and extension and the density of the fluid.
When the value of dyldx is not very small E is no longer constant, but is rather greater in compression and rather less in extension than -yP. This can be seen by considering that the relation between p and is given by a curve and not by a straight line.
The consequence is that the compression travels rather faster, and the extension rather slower, than at the speed found above.
The term Pv/V added up for a complete wave vanishes, for P/V is constant and Zv=o, since on the whole the compression equals the extension.
Giving a compression, and since the slope is steepest there, or - dyldx a maximum, the compression is also a maximum there.
It is obvious that the nodes are alternately in compression and extension, or vice versa, and that for 4X on each side of a node the motion is either to it on both sides or from it on both sides.
And what is true for the extreme points is true for the half periods of which they are the middle points; that is, heat given during the compression half aids the vibration, and during the extension half damps it.
Bridges may be classed as arched bridges, in which the principal members are in compression; suspension bridges, in which the principal members are in tension; and girder bridges, in which half the components of the principal members are in compression and half in tension.
Of the internal stresses, which balance the external forces, shows that most of the material should be arranged in a top flange, boom or chord, subjected to compression, and a bottom flange Or chord, subjected to tension.
20 shows a Fink truss, a characteristic early American type, with cast iron compression and wrought iron tension members.
For a bar subjected to alternate tension and compression of equal amount, A= 2 fmax.
O tons in verticals and long compression members.
For practical purposes it is accurate enough to consider the booms or chords as carrying exclusively the horizontal tension and compression and the web as resisting the whole of the vertical and, in a plate web, the equal horizontal shearing forces.
If A t A, are the cross sections of the tension and compression flanges or chords, and h the distance between their mass centres, then on the assumption that they resist all the direct horizontal forces the total stress on each flange is Ht=H,=M/h and the intensity of stress of tension or compression is f t = M/Ath, f c = M/Ach.
He sat rather sideways in the armchair next to the countess, arranging with his right hand the cleanest of gloves that fitted his left hand like a skin, and he spoke with a particularly refined compression of his lips about the amusements of the highest Petersburg society, recalling with mild irony old times in Moscow and Moscow acquaintances.