If the divisions are so fine that the coincidence is frequently doubtful, the best plan will be for the learner to get some acquaintance who is skilled in the use of instruments, and having set the instrument at hazard, to write down the readings of the verniers, and then request his friend to do the same; whenever there is any difference, he should carefully examine the doubtful one, and ask his friend to point out the minute peculiarities on which he founds his decision.

This should be repeated frequently; and after some practice, he should note how many times in a hundred his reading differs from his friend's, and also how many divisions they usually differ.
The next point is, to ascertain the precision with which the learner can bisect an object with the wires of the telescope.

This can be done without assistance.

It is not necessary even to adjust the instrument, but merely to point it to a distant object.

When it bisects any remarkable point, read off the verniers, and write down the result; then displace the telescope a little, and adjust it again.