This is not bad punctuation, for it conveys the meaning, which, however, is not difficult to obtain; but it is not good punctuation, for the marks do not group the words in accordance with the sense relations that exist between the groups.
If the sentence were divided into two parts by “but,” the but relation would exist between what follows and each of the groups of words coördinated by the conjunction “and.” Thus we would say, “The Society has expelled four of its members for unprofessional conduct, but has been unable to obtain enough evidence to convict them.” As this relation does not make sense, we know that the “but” relation exists between what follows it and what precedes it back to “and.” As the but relation does not extend beyond “and,” this fact should be shown by the mark, thus requiring a larger mark (semicolon) before “and.” But a semicolon before “and” would separate two closely connected groups (predicates),—“has expelled” and “has investigated.” It would also connect the second group with the third, making one larger group in the and relation with the first.
As the sense relations here require a grouping inconsistent with the grammatical relations, a change in the language becomes necessary before it can be properly punctuated:
23-1. The Society has expelled two of its members for unprofessional conduct; and it has investigated complaints against two other members, but has been unable to obtain enough evidence to convict them.
The insertion of “it” (a new subject) after “and,” and its omission after “but,” with the proper use of the semicolon, make clear the two things done by the Society, and make this clear by the proper grouping of words to show the unmistakable thought-grouping.
If we are required to punctuate language which we are not permitted to change, our punctuation may have to depart from our system, whether established by rule or by reason. A study of such punctuation will lead to a nice discrimination in both marks and relations. Our next sentence, with its different modes of punctuation, will illustrate the point. The sentence is given in three forms: (1) as it appeared in a literary journal; (2) as it is printed in the Common Version of the New Testament (2 Timothy i, 16); and (3) as it is printed in the Revised Version. We shall, however, not follow its division into two verses, as it appears in the Common Version of the Bible:
24. The Lord give mercy unto the house of Onesiphorus; for he oft refreshed me, and was not ashamed of my chain; but, when he was in Rome, he sought me out diligently, and found me.
24-1. The Lord give mercy unto the house of Onesiphorus; for he oft refreshed me, and was not ashamed of my chain: but, when he was in Rome, he sought me out very diligently, and found me.
24-2. The Lord grant mercy unto the house of Onesiphorus: for he oft refreshed me, and was not ashamed of my chain; but, when he was in Rome, he sought me out diligently, and found me.
In each of these three sentences the punctuation divides the language into three larger groups of words, two of which are subdivided by commas. In the second and third a colon indicates a second grouping of each sentence into two main parts, but not at the same point. If the semicolons and the colons were challenged for their meanings, the answers would show an interesting variety of grouping of words, as well as a variety of sense relations. Such a variety of punctuation is common only because the actual significance of marks, in their grouping and relational effects, has not been considered.
These sentences present the same problem, though somewhat further complicated, that was presented by Nos. 22 and 23. We have only to ask ourselves how far the but, for, and and relations extend. Do the marks so group the words as to indicate the sense relations by the grouping? Of course they do not, as is shown by the difference in the groupings. In No. 24 neither semicolon shows how far the for or the but relation extends; and therefore neither mark is an efficient sign-board. If challenged for a meaning, neither could give the reader an intelligent answer.