Excerpt from Periodic Variations in Efficiency: As Shown in Mental and Physical Tests Together With Some Weather Effects<br><br>Many studies have appeared which suggest the existence of periodic variations in both physical and mental activities during the year, during the day, and in conjunction with periodic changes in natural phenomena such as sunlight and temperature, but as yet the factors involved are but little understood. In order to assist in the solution of these complex problems, the author has attempted the following.<br><br>About the Publisher<br><br>Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com<br><br>This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.