Exercise 1.-If several watches are available, let one person tap sharply upon a desk with a pencil and let each of the others note the time by the minute hand to the nearest tenth of a minute and record the observations as follows: 2h. 44.5m. First tap. 2h. 46.4m. 1.9m. 2h. 44.9m. Second tap. 2h. 46.7m. 1.8m. 2h. 46.6m. Third tap. 2h. 48.6m. 2.0m. The letters h and m are used as abbreviations for hour and minute. The first and second columns of the table are the record made by one student, and second and third the record made by another.