Art. 17. Every vessel overtaking any other vessel shall keep out of the way of the said last-mentioned vessel. Art. 18. Where, by the above rules, one of two ships is to keep out of the way, the other shall keep her course, subject to the qualifications contained in the following Article. Art. 19. In obeying and construing these rules, due regard must be had to all dangers of navigation; and due regard must also be had to any special circumstances which may exist in any particular case rendering a departure from the above rules necessary, in order to avoid immediate danger. Art. 20. Nothing, in these rules, shall exonerate any ship, or the owner or master or crew thereof, from the consequences of any neglect to carry lights or signals, or of any neglect to keep a proper look-out, or of the neglect of any precaution which may be required by the ordinary practice of seamen or by the special circumstances of the case. Mr. Thomas Gray, one of the Assistant Secretaries to the Board of Trade (Marine Department), feeling how important it would be to have these rules impressed upon the minds of all navigators, and knowing what effect rhyme has in bringing at once to recollection, for instance, the number of days in each month, put with great tact and ingenuity these rules into verse, thus:— 1. Two steam-ships meeting. “When both side-lights you see ahead, Port your helm, and show your _red_.” 2. Two steam-ships passing. “_Green_ to _green_, or _red_ to _red_, Perfect safety—go ahead.” 3. Two steam-ships crossing. _Note._—This is the position of greatest danger; there is nothing for it but _good look-out, caution, and judgment_. “If to your starboard _red_ appear, It is your duty to keep clear; To act as judgment says is proper— To port, or starboard, back, or stop her! “But when upon your port is seen A steamer’s starboard light of _green_, There’s not so much for you to do, For _green_ to port keeps clear of you.” 4. All ships must keep a good look-out, and steam-ships _must stop, and go astern_, if necessary. “Both in safety and in doubt Always keep a good look-out; In danger, with no room to turn, Ease her—stop her—go astern!”