There are two great classes of sentences according to the general principles upon which they are founded. These are termed the loose and the periodic.
In the loose sentence the main idea is put first, and then follow several facts in connection with it. Defoe is an author particularly noted for this kind of sentence. He starts out with a leading declaration to which he adds several attendant connections. For instance in the opening of the story of Robinson Crusoe we read: "I was born in the year 1632 in the city of York, of a good family, though not of that country, my father being a foreigner of Bremen, who settled first at Hull; he got a good estate by merchandise, and leaving off his trade lived afterward at York, from whence he had married my mother, whose relations were named Robinson, a very good family in the country and from I was called Robinson Kreutznaer; but by the usual corruption of words in England, we are now called, nay, we call ourselves, and write our name Crusoe, and so my companions always called me."
In the periodic sentence the main idea comes last and is preceded by a series of relative introductions. This kind of sentence is often introduced by such words as that, if, since, because. The following is an example:
"That through his own folly and lack of circumspection he should have been reduced to such circumstances as to be forced to become a beggar on the streets, soliciting alms from those who had formerly been the recipients of his bounty, was a sore humiliation."
On account of its name many are liable to think the loose sentence an undesirable form in good composition, but this should not be taken for granted. In many cases it is preferable to the periodic form.
As a general rule in speaking, as opposed to writing, the loose form is to be preferred, inasmuch as when the periodic is employed in discourse the listeners are apt to forget the introductory clauses before the final issue is reached.
Both kinds are freely used in composition, but in speaking, the loose, which makes the direct statement at the beginning, should predominate.
As to the length of sentences much depends on the nature of the composition. However the general rule may be laid down that short sentences are preferable to long ones. The tendency of the best writers of the present day is towards short, snappy, pithy sentences which rivet the attention of the reader. They adopt as their motto multum in parvo (much in little) and endeavor to pack a great deal in small space. Of course the extreme of brevity is to be avoided. Sentences can be too short, too jerky, too brittle to withstand the test of criticism. The long sentence has its place and a very important one. It is indispensable in argument and often is very necessary to description and also in introducing general principles which require elaboration. In employing the long sentence the inexperienced writer should not strain after the heavy, ponderous type. Johnson and Carlyle used such a type, but remember, an ordinary mortal cannot wield the sledge hammer of a giant. Johnson and Carlyle were intellectual giants and few can hope to stand on the same literary pedestal. The tyro in composition should never seek after the heavy style. The best of all authors in the English language for style is Addison. Macaulay says: "If you wish a style learned, but not pedantic, elegant but not ostentatious, simple yet refined, you must give your days and nights to the volumes of Joseph Addison." The simplicity, apart from the beauty of Addison's writings causes us to reiterate the literary command—"Never use a big word when a little one will convey the same or a similar meaning."
Macaulay himself is an elegant stylist to imitate. He is like a clear brook kissed by the noon-day sun in the shining bed of which you can see and count the beautiful white pebbles. Goldsmith is another writer whose simplicity of style charms.
The beginner should study these writers, make their works his vade mecum, they have stood the test of time and there has been no improvement upon them yet, nor is there likely to be, for their writing is as perfect as it is possible to be in the English language.
Apart from their grammatical construction there can be no fixed rules for the formation of sentences. The best plan is to follow the best authors and these masters of language will guide you safely along the way.