One of the most common defacements which library books undergo is marking up the margins with comments or references in pencil. Of course no thoughtful reader would be guilty of this practice, but thoughtless readers are often in the majority, and the books they read or fancy that they read, get such silly commentaries on the margins as these: "beautiful," "very sad," "perfectly splendid," "I think Becky is horrid," or, "this book ends badly." Such vile practices or defacements are not always traceable to the true offender, especially in a circulating library, where the hours are so busy as to prevent the librarian from looking through the volumes as they come in from the readers. But if detected, as they may be after a few trials of suspected parties, by giving them out books known to be clean and free from pencil marks when issued to them, the reader should be required always to rub out his own marks, as a wholesome object-lesson for the future. The same course should be pursued with any reader detected in scribbling on the margin of any book which is being read within the library. Incorrigible cases, amounting to malicious marking up of books, should be visited by severe penalties--even to the denial of further library privileges to the offender. Not long ago, I bought at an auction sale a copy of the first edition of Tennyson's "In Memoriam," which was found on receipt to be defaced by marking dozens of verses in the margin with black lines drawn along them, absolutely with pen and ink! The owner of that book, who did the ruthless deed, never reflected that it might fall into hands where his indelible folly would be sharply denounced. The librarian or assistant librarian who will instinctively rub out all pencil marks observed in a library book deserves well of his countrymen. It is time well spent. The writing on book-margins is so common a practice, and so destructive of the comfort and satisfaction which readers of taste should find in their perusal of books, that no legitimate means of arresting it or repairing it should be neglected. In a public library in Massachusetts, a young woman of eighteen who was detected as having marked a library copy of "Middlemarch" with gushing effusions, was required to read the statute prescribing fine and imprisonment for such offenses, with very tearful effect, and undoubtedly with a wholesome and permanent improvement in her relations to books and libraries.