So much has been done of late towards developing the submarine vessel, that it appears that at present we are not very far from the practical solution of this interesting problem. Many engineers, as well as naval men and business people and others, must be interested in this matter, but as yet no work on this subject has appeared by which people, without spending too much time upon it, may be able to form an idea of what has already been done in this line, how the matter stands at the present moment, and what may probably be done in the future. It is the object of this little book to supply this want, and this, together with the interest I feel for this problem, must be my excuse for venturing to write on so difficult a subject.<br /><br />William Hovgaard (1887)