The best buildings in Havana are constructed of a very rich white limestone, soft and readily worked when fresh, but hardening and slightly darkening with age.
Hardening And Tempering Annealing >>
The shares, when made of the same material, required constant sharpening; this necessity was removed by the device, patented by Robert Ransome in 1803, of chilling and so hardening the under-surface of the share; the upper surface, which is soft, then wears away more quickly than the chilled part, whereby a sharp edge is always assured.
The color is fixed and the glaze set by secondary firing at a lower temperature than that necessary for hardening the p4te.
To this we may add a fantastic and absurd allegorization, the indiscriminate laudation of saints and martyrs, polemical strife, the hardening of the doctrine into dogma, the development of a narrow ecclesiasticism, and the failure of the missionary spirit in the orthodox section of the Eastern Church (as contrasted with the marvellous evangelistic activity of the Nestorians.
In this tribe are included Orthoptera with a large prothorax, whose eggs are enclosed in a common purse or capsule formed by the hardening of a maternal secretion.
Between 1860 and 1870 the invention of the Bessemer and open-hearth processes introduced a new class of iron to-day called " mild " or " carbon wcarbon steel," which lacked the essential property of steel, the hardening power, yet differed from the existing forms of wrought iron in freedom from slag, and from cast iron in being very malleable.
As a result, certain varieties, such as blister steel, are called " steel " solely because they have the hardening power, and others, such as low-carbon steel, solely because they are free from slag.
But the former lack the essential quality, slaglessness, which makes the latter steel, and the latter lack the essential quality, the hardening power, which makes the former steel.
Steel is iron which is malleable at least in some one range of temperature, and also is either (a) cast into an initially malleable mass, or (b) is capable of hardening greatly by sudden cooling, or (c) is both so cast and so capable of hardening.
That the ancients should have discovered an art of hardening bronze is grossly improbable, first because it is not to be hardened by any simple process like the hardening of steel, and second because, if they had, then a large proportion of the ancient bronze tools now known ought to be hard, which is not the case.
23-79) the relative value of different baths for hardening was known, and oil preferred for hardening small tools.
This change from austenite to ferrite and cementite, from the y through the # to the a state, is of course accompanied by the loss of the " hardening power," i.e.
The power of being hardened by sudden cooling, because the essence of this hardening is the retention of the (3 state.
As such steel cools slowly past Ar3, Ar 2 and Ar 1, it loses its hardening power progressively.
Thermal Treatment.-The hardening, tempering and annealing of steel, the chilling and annealing of cast iron, and the annealing of malleable cast iron are explained readily by the facts just set forth.
The hardening of steel consists in first transforming it into austenite by heating it up into region 4 of fig.
The degree of hardening which the steel undergoes increases with its carbon-content, chiefly because, during sudden cooling, the presence of carbon acts like a brake to impede the transformations, and thus to increase the quantity of 0-iron caught in transit, but probably also in part because the hardness of this 0-iron increases with its carbon-content.
Like the hardening of steel, it hinders the transformation of the austenite, whether primary or eutectic, into pearlite+cementite, and thus catches part of the iron in transit in the hard a state.
Its combination of ductility with strength and hardening power has given it very extended use for the armour of war-vessels.
The plate is then by Krupp's process heated so that its impact face is above while its rear is below the hardening temperature, and the whole is then cooled suddenly with sprays of cold water.
Under these conditions the hardness, which is very extreme at the impact face, shades off toward the back, till at about quarter way from face to back all hardening ceases, and the rest of the plate is in a very strong, shock-resisting state.
The hardening of the extremities of the fibro-vascular tissue is the cause of the spiny margin of many leaves, such as the holly, of the sharp-pointed leaves of madder, and of mucronate leaves, or those having a blunt end with a hard projection in the centre.
Tannin is a hardening and astringent substance, and in large quantities impairs digestion.
Subsequent hardening of the mortar is caused by the gradual absorption of carbonic acid from the air by the lime, a skin of carbonate of lime being formed; but the action is superficial.
It is generally admitted that the aluminate is the chief agent in the first setting of the cement, and that its ultimate hardening and attainment of strength are due to the tricalcium silicate.
One of the most valuable characteristics of the iron alloys is their capacity for hardening, which they owe in the main to the presence of certain small percentages of carbon relatively to minute quantities of other elements: as manganese, tungsten, nickel and others of less importance.
The capacity for hardening is an invaluable property not only in regard to cutting-tools, but also in prolonging the life of parts subjected to severe friction.
The tissues and fluids are treated by various histological methods, but, to speak generally, examination is made either in films smeared on thin cover-glasses and allowed to dry, or in thin sections cut by the microtome after suitable fixation and hardening of the tissue.
Silicic hardening does not begin till the full height is nearly attained.
Generally speaking they do not share in the special modifications of the flowering glumes, and rarely themselves undergo modification, chiefly in hardening of portions (Sclerachne, Manisuris, Anthe- phora, Peltophorum), so as to afford greater protection to the flowers or fruit.
Types of muffle furnaces are figured in the article Annealing, Hardening And Tempering.
Hardening, Jenn turned away and retreated through the forest and rocks to the compound.
The cathedral is faced with pale grey limestone, easily chiselled, but hardening on exposure.
The course of the ensuing campaigns was to reveal the hardening of his mental powers.
21, d) - such as may be noticed in the majority of the Lepidoptera - whose appendages are closely and immovably pressed to the body by a general hardening and fusion of the cuticle.
His character was hardening, and he deliberately adopted the most barbarous expedients for converting the Augustan Poles to his views.
The rock on the surface is as hard as flint, but underneath it gradually softens and furnishes an admirable stone for building which can be sawn into blocks of any size, hardening on exposure to the atmosphere.
Resina, probably Latinized from Greek prpivri, resin), a secretion formed in special resin canals or passages of plants, from many of which, such as, for example, coniferous trees, it exudes in soft tears, hardening into solid masses in the air.
Another point to which attention is directed is the exceptionally great effect which hardening has upon the magnetic properties of chrome steel; one specimen had a coercive force of 9 when annealed, and of no less than 38 when oilhardened.
Thus its non-liability to freeze (when not absolutely anhydrous, which it practically never is when freely exposed to the air) and its nonvolatility at ordinary temperatures, combined with its power of always keeping fluid and not drying up and hardening, render it valuable as a lubricating agent for clockwork, watches, &c., as a substitute for water in wet gas-meters, and as an ingredient in cataplasms, plasters, modelling clay, pasty colouring matters, dyeing materials, moist colours for artists, and numerous other analogous substances which are required to be kept in a permanently soft condition.