The first the chapters of the following treatise are intended for beginners; and nine of them are reprinted with but slight alterations from a series of articles on Logic contributed by me to Our School Times, a periodical then attached to Monaghan Diocesan School. They were written at the request of Dr. Hime, the Head Master, who was also the editor of the periodical in question, with the object of making the subject intelligible to advanced school-boys and other beginners who might be among the readers of the paper. Those who desire to become acquainted with the fundamental principles of Deductive Logic only may confine their attention to these chapters; but it will be seen that the subsequent chapters intended for those who desire to carry their studies farther occupy about two-thirds of the book. I do not think the order in which the various matters treated of are dealt with will occasion any embarrassment to the student who reads on to the end; while for him who means to stop at the elementary principles no other order would have been suitable.