The Elements of Style ( Fourth Edition ). The griffin classics

      6. Do not break sentences in two.

      In other words, do not use periods for commas.

      I met them on a Cunard liner several years ago. Coming home from Liverpool to New York.

      He was an interesting talker. A man who had traveled all over the world, and lived in half a dozen countries.

      In both these examples, the first period should be replaced by a comma, and the following word begun with a small letter.

      It is permissible to make an emphatic word or expression serve the purpose of a sentence and to punctuate it accordingly:

      Again and again he called out. No reply.

      The writer must, however, be certain that the emphasis is warranted, and that he will not be suspected of a mere blunder in punctuation.

      Rules 3, 4, 5, and 6 cover the most important principles in the punctuation of ordinary sentences; they should be so thoroughly mastered that their application becomes second nature.

      7. A participial phrase at the beginning of a sentence must refer to the grammatical subject.

      Walking slowly down the road, he saw a woman accompanied by two children.

      The word walking refers to the subject of the sentence, not to the woman. If the writer wishes to make it refer to the woman, he must recast the sentence:

      He saw a woman, accompanied by two children, walking slowly down the road.

      Participial phrases preceded by a conjunction or by a preposition, nouns in apposition, adjectives, and adjective phrases come under the same rule if they begin the sentence.

      On arriving in Chicago, his friends met him at the station.

       When he arrived in Chicago, his friends met him at the station.

      A soldier of proved valor, they entrusted him with the defence of the city.

       A soldier of proved valor, he was entrusted with the defence of the city.

      Young and inexperienced, the task seemed easy to me.

       Young and inexperienced, I thought the task easy.

      Without a friend to counsel him, the temptation proved irresistible.

       Without a friend to counsel him, he found the temptation irresistible.

      Sentences violating this rule are often ludicrous.

      Being in a dilapidated condition, I was able to buy the house very cheap.