| I. | Rhyolite, Telki Banya, Hungary. |
| II. | Rhyolite, do. Mafahlid, Iceland. |
| III. | Rhyolite, do. Omahu, New Zealand. |
| IV. | Pantellarite, Pantellaria. |
| V. | Quartz-keratophyre, Muhlenthal, Hara. |
| VI. | Comendite, Sardinia. |
We note in the rhyolites I.–III. the very high silica, with alkalis and alumina also in considerable amount, while lime, magnesia and iron are very low. In the pantellarite, keratophyre and comendite the silica tends to be less abundant, while the alkalis, especially soda, increase; they have less alumina but are richer in iron and magnesia. It is easy to see why the latter types contain less quartz, felspars often very rich in soda, and femic minerals which contain iron and alkalis in notable amounts such as aegirine, riebeckite and arfvedsonite. (J. S. F.)
RHYTHM (Greek ῥυθμὸς, from ῥεῖν, to flow), the measured
flow of movement, or beat, in verse, music or by analogy in
other Connexions, e.g. “rhythm of life.” The early critic of
prosody, Aristoxenus, distinguished its the three elements out of
which rhythm is composed, the spoken word, λέξις, the tune of
music and song, μέλος, and the bodily motion, κίνησις σωματική,
The art of the early Greek poets was devoted to a harmonious
combination of these three elements, language,
instrument and gesture uniting to form perfect rhythm. Aristoxenus
proceeds to deflne the rhythm so produced as an arrangement
of time-periods, τάξιν χρόνων, but other early theorists
make not the time but the syllable the measurement of poetic
speech. Both music and poetry depend, and have depended
from the earliest times, on rhythm. But in music melody and
harmony have to be taken into consideration, whereas in poetry
the rhythmical value of the tone is modified by the imaginative
value and importance of the words themselves. In earliest
times the fundamental unity of the two arts was constantly
manifest, but as the world has progressed, and they have
ramified into countless forms, the difference between them has
been emphasized more and more.
Rhythm in Verse.—Professor Jakob Minor has adduced a figure, valuable in helping us to realize what poetic rhythm is, when he remarks that to strike a bell twelve times, at exactly equal intervals, is to produce what may be called, indeed, a rhythmic effect, but not to awaken anything resembling the sensation of poetical rhythm. Into the idea of poetic rhythm enters an element of life, of pulse, of a certain inequality of time based upon an equality of tone. Rhythm ceases to be poetic, rhythm if it is mechanical or lifeless. Aristotle, from whom a definition might “be expected, is very vague in dealing with the subject, and most of the old rhetorical writers darken counsel with statements that are obscure or irrational. The fact is that rhythm is an expression of the instinct for order in sound which naturally governs the human ear, and little practical knowledge is gained by following Suidas when he says that rhythm is the father of metre, or Quintilian in his epigram that rhythm is male and metre is female., These definitions arise from a rhetorical desire to measure a delicate instinct by rule, of three, and, as a matter of fact, Greek criticism on this subject often lost itself in arithmetical absurdities. It is sufficient to say that rhythm is the law which governs the even and periodical progress of sounds, in harmony with(the exigencies of human emotion. For the passions, as expressed in verse, various movements are appropriate. joy demands that the voice should leap and sing; sorrow that it should move solemnly and slowly; and poetry, which is founded on rhythm, requires that the movement of words should respond to this instinctive gradation of sounds. The finer the genius of the metrist the more exquisitely does his rhythm convey, as upon an instrument, the nature of;the passion which burdens his verses. Ecstasy takes a quick, eager, rising movernent:—
| “Give him the nectar! |
| Pour out for the poet, |
| Hebe, pour free! |
| Quicken his eyes with celestial dew, |
| That Styx the detested no more he may view.” |
Mystery and suspense demand a faint, languid and throbbing movement:—
“There is not wind enough in the air
To move away the ringlet curl
From the lovely. lady’s cheek—
There is not wind enough to twirl
The one red leaf, the last of its clan,
That dances as often as dance it can.”
An I overpowering sadness interprets itself in rhythm* that is full and slow and emphatic:—
“My genial spirits fail,
And what can these avail
To lift the smothering weight from off my breast?
It were a vain endeavour,
Though I should gaze for ever
On that green light that lingers in the west:
I may not hope from outward forms to win
The passion and the life, whose fountains are within.”
The rhythm so produced, intimately linked, almost beyond the disintegrating power of analysis, with human feeling, may depend” either on accentuation or quantity. The latter forms the principle upon which all classic metre was composed, while the former is dominant in nearly every description of modern. verse. Greek. and Latin verse depends entirely upon the relation of syllables, long or short. It was a question of time with the ancients, of stress or, weight with us. It is an error to say, as is often done, that ancient verse did not recognize accent, and that in modern verse there is no place for quantity. These statements are generally true, but there are various exceptions to both rules. Schipper, in his Englische Metrik, specially points out that “long and short syllables have no constant length, no constant relation, but they depend on their place in the verse, and on the context; though they do not determine the rhythm of verse, they still act as regulators of our metre in a very important degree.” Pauses, take an essential importance in the construction of modern rhythm, of the variety and vitality of which they are the basis. They are introduced for the purpose of relieving the monotony of successive equal groups of syllables. The pause often takes the place of a light syllable, and there are instances in the verse of, Shakespeare and Milton where it is even allowed to fill up the space of a heavy syllable. But still more often the pause does not imply the dropping of a syllable at all, but simply dictates a break in the sound, equivalent to a break in the sense. The following extract from a “Psalm” in Crashaw’s Steps to the Temple (1646), in when the pauses are numerous and energetic, will exemplify the variety of this artifice:—
“On the proud banks of great Euphrates’ flood, | |
In the blank verse of Milton the free use of pauses constitutes the principal element in the amazing metrical art of the poet, and is the source of the sublime originality of his music. In speaking of rhythm, it is customary to think of the formal rules which govern the fixed cadence of feet in poetry, but there is also a rhythm in prose, which imitates the measured movements of the body in Stately speech. According to Ronan, the rhythm of the ancient poetry of the Hebrews is solely founded on this prose movement, which differs, in fact, from that of modern European poetry merely in its undefined and indeterminate character.
See J. Minor, Neuhochdeutsche Metrik (Strassburg, 1893); W. Christ, Die Metrik der Greichen (Leipzig, 1874); Roderick Benadix, Das Wesen des deutschen Rhythmus (Leipzig, 1862) Jakob Schipper, Englische Metrik (Leipzig, 1895); Edwin Guest, History of English Rhythms (London, 1838; 2nd ed., 1882); Théodore de Banville, Petit Traité de la poésie française (Paris, 1881); F. B. Gummere, Handbook of Poetics (Boston, 1902). (E. G.)
Rhythm in Music.—The rhythm of modern music began to develop through -the attempts of learned medieval musicians to adapt the rhythms of spoken language to the necessities of choral singing; but before the process had gone far, certain much more ancient and powerful principles, always manifest intfolk-song and dance, gained ascendancy, so that even the
