Another fact that makes it easy for the eye to recognize a paragraph is that it frequently does not close with the end of a line.
When, therefore, you look at a piece of printed or written composition, you see at once that you are to receive a certain number of thoughts or ideas, each of which is placed in a section or paragraph by itself. In listening to an address or oration you notice the separation between the thoughts by the fact that the speaker usually makes a pause of several seconds to indicate that he has finished the expression of one thought and is now ready to pass on to another.
Note.—In writing a long conversation, it is usually customary to make each speech of each person a paragraph by itself, even if it consists of only a few words. This is because it is of the utmost importance, in reading an account of a conversation, to know just who is speaking.
10. The Beginning.—We group our sentences. But how shall we begin? What sentences shall come first? Usually we shall express our thoughts most clearly if we begin with a sentence that shows in brief what the whole paragraph is about. This is sometimes called the topic sentence, because it is the sentence that states the topic or central idea of the paragraph.
Examples. 1. To the simple-hearted folk who dwelt in that island three thousand years ago, there was never a sweeter spot than sea-girt Ithaca. Rocky and rugged though it may have seemed, yet it was indeed a smiling land embosomed in the laughing sea. There the air was always mild and pure, and balmy with the breath of blossoms; the sun looked kindly down from a cloudless sky, and the storms seldom broke the quiet ripple of the waters which bathed the shores of that island home. On every side but one, the land rose straight up out of the deep sea to meet the feet of craggy hills and mountains crowned with woods. Between the heights were many narrow dells green with orchards, while the gentler slopes were covered with vineyards, and the steeps above them gave pasturage to flocks of long-wooled sheep and mountain-climbing goats.—James Baldwin: A Story of the Golden Age.
[Here the first sentence shows that the paragraph is to be about the beauty of the island.]
2. Upon the ridge above our tent was a third tiny clearing, where some trappers had once made their winter camp. It was there that I watched the rabbits one moonlight night from my seat on an old log, just within the shadow at the edge of the opening. The first arrival came in with a rush. There was a sudden scurry behind me, and over the log he came with a flying leap that landed him on the smooth bit of ground in the middle, where he whirled around and around with grotesque jumps, like a kitten after its tail. Only Br'er Rabbit's tail was too short for him ever to catch it; he seemed rather to be trying to get a good look at it. Then he went off helter-skelter in a headlong rush through the ferns. Before I knew what had become of him, over the log he came again in a marvelous jump, and went tearing around the clearing like a circus horse, varying his performance now by a high leap, now by two or three awkward hops on his hind legs, like a dancing bear. It was immensely entertaining.—William J. Long: Ways of Wood Folk.
[Here the first two sentences show that the paragraph is to be about watching rabbits in a clearing by moonlight.]