This work, originally designed as a book of instruction for the cadets of the Military Academy, has, since my separation from the department of artillery, been extended beyond the limits at first proposed, with a view of spreading information not popularly accessible, upon a subject of the first importance to our national defense. It is submitted to my brother officers, trusting that many allowances will be made for its defects, and that some one more capable of doing justice to the subject will be induced to offer to the service, and to our militia -- on whom, in the event of war, the principal defense of our large fortifications must devolve -- a more complete system of instruction than I have been able to furnish. Where translations have been made, it has been my endeavor to select such portions as are or may be applicable to our own service, leaving out those peculiar to the foreign.