Among the ammonites the loss of power to coil the shell is one feature of racial old age, and in others old age is accompanied by closer coiling and loss of surface ornamentation, such as spines, ribs, spirals; while in other forms an arresting of variability precedes extinction.
They are unusually interesting from the fact that many of the exposed slabs in the walls of the chambers are ornamented with spirals and other devices, rudely incised.
(4) On Spirals (Peri helikon) is a book of twenty-eight propositions.
The tree is tapped either in the same manner as the Hevea, or by encircling the tree with a simple spiral cut at an inclination of 45°, or by two parallel spirals if the tree be large.
The have been identified by Helbig with small spirals of gold wire, such as are found in early Etruscan tombs lying near the head of the skeleton.
Such spirals were used in early Athens to confine the back hair, and this fashion may therefore be identified as the Kpc f3vXos.
Uredospores, septa of Basidiomycetes), spirals, reticulations, rings, &c. (capillitium fibres of Podaxon, Calostoma, Battarrea), occur as in the vessels of higher plants, while sculptured networks, pittings and so forth are as common on fungus-spores as they are on pollen grains.
But in such cases a series of secondary spirals or parastichies are seen running parallel with each other both right and left, which to a certain FIG.
The circles in the centre indicate a rectilinear series of indicate the five turns of the spiral, scales and two lateral secondand show the insertion of each of the ary spirals, one turning from leaves.
Later we find two periods of zigzag designs in south Germany with an intermediate stage of spirals and wavy lines, while in north and east Germany the so-called string-ornamentation predominates.
They introduced a special style of ornament ("geometric") instead of that of the Bronze Age, characterized by spirals and marine animals and plants.
The latter are formed of two spirals of wire, sometimes four such spirals being used, whilst there were also brooches in animal forms, one of the latter being found with a bronze sword.
Divisions perpendicular to the long axis: - Vibrio (Muller-Ldffler), commashaped, motile, monotrichous; Spirillum (Ehrenb.), more strongly curved in open spirals, motile, lopho trichous; Spirochaete (Ehrenb.), spirally coiled in numerous close turns, motile, but apparently owing to flexile movements, as no cilia are found.
The ornamentation of the period is as a rule confined to spirals, bosses and concentric circles.
Superimposed sections of rightand left-handed quartz, as may sometimes be present in sections of twinned crystals, exhibit Airy's spirals in the polariscope.
With two plates of equal thickness and of opposite rotations, the pattern consists of a series of circles and of four similar spirals starting from the centre, each spiral being turned through 90° from that adjacent to it.
When the light is circularly polarized or circularly analysed, a single plate gives two mutually enwrapping spirals, and similar spirals in circularly polarized light are obtained with plates of an active biaxal crystal perpendicular to one of the optic axes.
Aceae, where the parts are in spirals (acyclic).
This idea that material representation involves a profanation of divine personages, while disallowing all religious art which goes beyond scroll-work, spirals, flourishes and geometrical designs, yet admits to the full of secular art; and accordingly the iconoclastic emperors replaced the holy pictures in churches with frescoes of hunting scenes, and covered their palaces with garden scenes where men were plucking fruit and birds singing amid the foliage.
In his investigations respecting cycloidal lines and various spiral curves, his attention was directed to the loxodromic and logarithmic spirals, in the last of which he took particular interest from its remarkable property of reproducing itself under a variety of conditions.
When an engineer has to construct a railway up a hill having a still steeper slope, he must secure practicable gradients by laying out the line in ascending spirals, if necessary tunnelling into the hill, as on the St Gothard railway, or in a series of zigzags, or he must resort to a rack or a cable railway.