And here are reddish stains, made by the impact of that cuff with the tan-bark of the riding hall.
Here are slips of paper on which the main features of the hardest math.

problems of each day have been noted down, ready for writing on a cuff.

Here is the water-proof ink and the pen with which the writing on the cuff was done.

And here are some other slips of paper, evidently older, on which other problems have been written out more fully.

These older slips of paper contain problems of last November and early December---the time when Prescott was in his deep trouble.