Here is a pocket reading-lamp which you can hook on the carriage lining.

This notebook can be fixed to the board with an india-rubber band--thus.

You observe that the thoughtful Polton has stuck a piece of thread on the glass of the compass to serve as a lubber's line.

This is how you will proceed.

As soon as you are locked in the carriage, light your lamp--better have a book with you in case the light is noticed--take out your watch and put the board on your knee, keeping its long side exactly in a line with the axis of the carriage.