ordinary slate nail and a common picture frame nail with a brass head.
The latter indicates work to be done, the former work done.

To prepare the board for service, brass headed nails are placed opposite
each experiment, and below the names, care being taken not to have more
than one nail in the same horizontal row, unless it is intended that two
persons or more are to work upon the same experiment.

There will be no conflict when the brass nails occupy diagonal lines. If
they do not, a glance will show the fact.

After an experiment has been performed and a report made upon the usual
blank, the brass nail is removed and a slate nail put in its place.

The board will show by the slate nails what work has been done by each
student, by the brass nails what is yet to be done, and by the empty
holes, experiments which have been omitted or are yet to be assigned. A
slate nail opposite an experiment card indicates that that experiment
may now be assigned to another person.

It is evident that the schedule for a whole term may be arranged in a
few minutes and that the daily changes require very little time.

The board is hung in a convenient place. The student as he enters the
laboratory looks for his name on the upper cards and under it for the
first brass nail in the vertical column: to the left he finds the
experiment card. On the left hand end of the slip he sees the book
references, on the right hand end a number--39 in the sample card given
above. Knowing the number, he proceeds to a desk and finds a box
numbered in the same manner. He removes the box from the closet. On the