XXIV
CHEMICALS AS DISINFECTANTS AND PRESERVATIVES
NITROGEN AND ITS RELATION TO PLANTS
HOW ELECTRICITY MAY BE MEASURED
HOW ELECTRICITY IS OBTAINED ON A LARGE SCALE
By JOHN GAYLORD COULTER, Ph. D.
SHARPE'S LABORATORY MANUAL IN BIOLOGY
PREFACE
This book is not intended to prepare for college entrance examinations; it will not, in fact, prepare for any of the present-day stock examinations in physics, chemistry, or hygiene, but it should prepare the thoughtful reader to meet wisely and actively some of life's important problems, and should enable him to pass muster on the principles and theories underlying scientific, and therefore economic, management, whether in the shop or in the home.
We hear a great deal about the conservation of our natural resources, such as forests and waterways; it is hoped that this book will show the vital importance of the conservation of human strength and health, and the irreparable loss to society of energy uselessly dissipated, either in idle worry or in aimless activity. Most of us would reproach ourselves for lack of shrewdness if we spent for any article more than it was worth, yet few of us consider that we daily expend on domestic and business tasks an amount of energy far in excess of that actually required. The farmer who flails his grain instead of threshing it wastes time and energy; the housewife who washes with her hands alone and does not aid herself by the use of washing machine and proper bleaching agents dissipates energy sadly needed for other duties.
The Chapter on machines is intended not only as a stimulus to the invention of further labor-saving devices, but also as an eye opener to those who, in the future struggle for existence, must perforce go to the wall unless they understand how to make use of contrivances whereby man's limited physical strength is made effective for larger tasks.
The Chapter on musical instruments is more detailed than seems warranted at first sight; but interest in orchestral instruments is real and general, and there is a persistent desire for intelligent information relative to musical instruments. The child of the laborer as well as the child of the merchant finds it possible to attend some of the weekly orchestral concerts, with their tiers of cheap seats, and nothing adds more to the enjoyment and instruction of such hours than an intimate acquaintance with the leading
