In other species the summits of the ridges are divided into conical cusps, and may have accessory cusps clustering around them (as in M.
When the summits of these are worn by mastication their surfaces present circles of dentine surrounded by a border of enamel, and as attrition proceeds different patterns are produced by the union of the bases of the cusps, a trefoil form being characteristic of some species.
The snow-covered summits of the Elbruz are visible to the south.
The northern portion of it consists of a lofty ridge with two summits, the westernmost of which is occupied by the modern town (985 ft.), while the easternmost, which is slightly higher, bears the name of Rock of Athena, owing to its identification in modern days with the acropolis of Acragas as described by Polybius, who places upon it the temple of Zeus Atabyrius (the erection of which was attributed to the half mythical Phalaris) and that of Athena.'
On the north both summits are defended by cliffs; on the south the ground slopes away somewhat abruptly from the eastern summit towards the plateau on which the town stood, while the western summit is separated from this plateau by a valley traversed by a branch of the Hypsas [mod.
By the ranges of Grammos and Pindus; the entire chain, a prolongation of the Alpine systems of Bosnia and Dalmatia, may be described as the backbone of the peninsula; it forms the watershed between the Aegean and the Adriatic, and culminates in the lofty peak of Liubotrn, near Kalkandele, one of the highest summits in south-eastern Europe (8858 ft.).
South of the Drin is another complex mountain system, including the highlands inhabited by the Mirdites and the Mat tribe; among the principal summits are Deia Mazzuklit, Mal-i Vels, Kraba, Toli and Mnela.
On the south-eastern frontier the French Alps, which include Mont Blanc (15,800 ft.), and, more to the south, other summits over 11,000 ft.
In the southern and most elevated portion of the range there are several summits exceeding 5500 ft.
Two miles north-east is the famous Silla de Caracas, whose twin summits, like a gigantic old-fashioned saddle (silla), rise to an elevation of 8622 ft.; and the Naiguete, still farther eastward, overlooks the valley from a height of 9186 ft.
Summits of the lower incisors, before they are worn, with a deep transverse groove, dividing it into an anterior and a posterior cusp. Canines long, strong and conical.
Their summits stand out gaunt and lonely in an unbroken solitude.
A verdure of herbage clothes the valleys that have been scooped from the summits downwards.
The mountains of the north-east, on the contrary, are clothed to their summits with a rich and varied flora.
The surface on the whole is hilly and is partly occupied by offshoots of the Thuringian Forest; the highest summits are found in the eastern half, where the Kieferle reaches 2849 ft.
The descent from the summits of the range into the plain is somewhat less abrupt on the western than it is on the eastern side, and between the foot of the mountains and the Strait of Malacca the largest known alluvial deposits of tin are situated.
High, considerable areas are above 2500 ft., and the following summits exceed 4000 ft.: Mount Mansfield, 4364 ft.; Killington Peak, 4241 ft.; Camel's Hump, 4088 ft.; Mount Lincoln, 4078 ft.; and Jay Peak, 4018 ft.
The forms of Vermont's mountains, even to the highest summits, were to a great extent rounded by glaciation, but as the rocks vary much in texture and are often steeply inclined, stream erosion has cut valleys deep and narrow, often mere gorges.
In the summits of the Kushlar Dagh, Karluk Dagh and KaraBalkan.
Its outline is very irregular; from the centre of the town, at the junction of several ridges, parts of it extend for a considerable distance along their summits, being divided from one another by deep valleys.
This is the highest point in the northern Apennines, and belongs to a group of summits of nearly equal altitude; the range which is continued thence between Tuscany and what are now known as the Emilian provinces presents a continuous ridge from the mountains at the head of the Val di Mugello (due north of Florence) to the point where they are traversed by the celebrated Furlo Pass.
The line of the highest summits and of the watershed ranges is about 30 to 40 m.
Farther south no very lofty summits are found till we come to the group of Monti del Matese, in Samnium (6660 ft.), which according to the division here adopted belongs to Southern Italy.
Nor do the highest summits form a continuous ridge of great altitude for any considerable distance; they are rather a series of groups separated by tracts of very inferior elevation forming natural passes across the range, and broken in some places (as is the case in almost all limestone countries) by the waters from the upland valleys turning suddenly at right angles, and breaking through the mountain ranges which bound them.
Two of the summits of this group, the Pizzo d'Uccello and the Pania della Croce, attain 6155 and 6100 ft.
The Arno, which has its source in the Monte Falterona, one of the most elevated summits of the main chain of the Tuscan Apennines, flows nearly south till in the neighborhood of Arezzo it turns abruptly north-west, and pursues that course as far as Pontassieve, where it again makes a sudden bend to the west, and pursues a westerly course thence to the sea, passing through Florence and Pisa.
From the neighborhood of Potenza, the main ridge of the Apennines is continued by the Monti della Maddalena in a direction nearly due south, so that it approaches within a short distance of the Gulf of Policastro, whence it is carried on as far as the Monte Pollino, the last of the lofty summits of the Apennine chain, which exceeds 7000 ft.
In the natural process of growth, the gap must necessarily be wider between the summits of the twigs than lower down, and, instead of imagining " missing links," it is necessary to trace each separate branch as low down as possible, and to institute the comparisons between the lowest points that can be reached.
Except such as are of coral formation, the Antilles are hilly, not to say mountainous, their summits rising in places to an elevation of 8000 ft., and nearly all, prior to their occupation by Europeans, were covered with luxuriant forest, which, assisting in the collection and condensation of the clouds brought by the trade winds, ensured its own vitality by precipitating frequent and long-continued rains; upon the fertile soil.
The most easterly of these chains, that forming the Pays de Gex in the extreme north-east of the department, contains the Cret de la Neige (6653 ft.) and other of the highest summits in the whole range.
In the north, where the province borders Semipalatinsk, it includes the western parts of the Tarbagatai range, the summits of which (10,000 ft.) do not reach the limit of perpetual snow.
The zone of highlands throughout Bosnia and Herzegovina reaches a mean altitude of 1500 ft., while summits of more than 4000 ft.
They descend in parallel ridges of grey Karst limestone, south-westwards to the sea; their last summits reappear in the multitude of rocky islands along the Dalmatian littoral.
The summits are generally well rounded, while the lower slopes are often steep. Frequent broad intervals of low upland or low level plain extend from sea to sea between and around the mountains.
In thickness, they probably at one time covered the whole island except the summits of the Sierra Maestra, where they have been observed, resting upon the older rocks, up to a height of 2300 ft.
In each direction the country falls away in a succession of minor undulations, the summits of the ridges being occupied by the streams and bayous.
Nearly the whole of the Riesenkamm and the western portion of the southern chain are granite; the eastern extremity of the main ridge and several mountains to the south-east are formed of a species of gneiss; and the greater part of the Bohemian chain, especially its summits, consists of mica-slate.
The Schneekoppe and other summits are annually visited by a considerable number of travellers, notably the spas of Warmbrunn (near Hirschberg) and Flinsberg on the Gneis, and Gorbersdorf, known as a climate health resort for consumptives.
But the lakes show a wonderful variety of character, from open expanse and steep rock-bound shores to picturesque island-groups and soft wooded banks; while the mountains have always a remarkable dignity, less from the profile of their summits than from the bold sweeping lines of their flanks, unbroken by vegetation, and often culminating.
It drains north by St John's Vale into the Greta, north of which again rises a mountain-group of which the chief summits are Saddleback or Blencathra (2847 ft.) and the graceful peak of Skiddaw (3054).
It soon becomes the boundary for a while between the departments of the HautesAlpes and of the Basses-Alpes, and receives successively the considerable Ubaye river, flowing from near the foot of Monte Viso past Barcelonnette (left), and then the small stream of the Luye (right), on which, a few miles above, is Gap. It enters the Basses-Alpes shortly before reaching Sisteron, where it is joined (right) by the wild torrent of the Busch, flowing from the desolate region of the Devoluy, and receives the Bleone (left) (on which Digne, the capital of the department, is situated) and the Asse (left), before quitting the department of the Basses-Alpes just as it is reinforced (left) by the Verdon, flowing from the lower summits of the Maritime Alps past Castellane.
This paper is principally based on the following general theorem, which is a remarkable extension of Pascal's hexagram: "If a polygon move so that each of its sides passes through a fixed point, and if all its summits except one describe curves of the degrees m, n, p, &c., respectively, then the free summit moves on a curve of the degree 2mnp. ..