they may be quite unusable and
necessitate going through the expensive process of observation all
over again. Dr. Taylor has stated that during his earlier
experiences he was obliged to throw away a large quantity of time
study data, because they were not in sufficient detail and not
recorded completely enough to enable him to use them after a lapse
of a long period from the time of their first use. No system of time
study, and no individual piece of time study, can be considered a
success unless by its use at any time, when new, or after a lapse of
years, an accurate prediction of the amount of work a man can do can
be made.

All results attained should invariably be preserved, whether
they appear at the moment to be useful or valuable or not. In time
study in the past it has been found, as in the investigations of all
other sciences, that apparently unimportant details of today are of
vital importance years after, as a necessary step to attain, or
further proof of a discovery. This was exemplified in the case of
the shoveling experiment of Dr. Taylor. The laws came from what was
considered the unimportant portion of the data. There is little so
unimportant that time and motion study would not be valuable. Just
as it is a great help to the teacher to know the family history of
the student, so it is to the one who has to use time and motion
study data to know all possible of the hereditary traits,
environment and habits of the worker who was observed.

SPECIALIZED STUDY IMPERATIVE.--As an illustration of the field
for specialized investigation which motion study and time study
present, we may take the subject of fatigue. Motion Study and Time
Study aim to show,

1. the least fatiguing method of getting least waste.
2. the length of time required for a worker to do a
certain thing.
3. the amount of rest and the time of rest required to
overcome fatigue.

Dr. Taylor spent years in determining the percentage of rest
that should be allowed in several of the trades, beginning with
those where the making of output demands weight hanging on the arms;
but there is still a great amount of investigation that could be
done to advantage to determine the most advisable percentage of rest
in the working day of different lengths of hours. Such investigation
would probably show that many of our trades could do the same amount
of work in fewer hours, if the quantity and time of rest periods