MEASUREMENTS FOR THE HOUSEHOLD I. INTRODUCTION 1. Purpose of this Circular The purpose of this circular is (1) to give information as to units, methods, and instruments of measurement useful in household activities, (2) to describe available means of assuring correct quantity in articles bought by weight and measure, and (3) to give other facts of interest which would awaken an appreciation of the rôle of measurement in daily life. In the scientific investigations of numerous questions the Bureau of Standards has accumulated general information which may be known to the industries concerned, and hence of less novelty to them, but is often of great value and importance to the genera public. For example, watchmakers are familiar with the construc-1 tion and adjustment of watches and clocks, and the best methods of caring for them, but the ordinary purchaser who uses them is often at a loss to obtain the most elementary knowledge of how to properly care for them. In the same way, to electrical and gas engineers information given in this circular is everyday knowledge, but the householder, while deeply concerned about the indications of his meters and the quality of the gas supplied to him, often finds it difficult, if not impossible, to secure simple technical information that is often of great value to him. It was with the purpose of making the results of the work of the Bureau available to the public in so far as this work is related to the work of the household that this circular has been prepared. 2. Rôle of Measurement in Daily Life Household measurements suggest many interesting phases of the art of measurement. The significance of measurements in our civilization and their effect upon everyday life may not be fully appreciated. From the beginning of life measurement is important. The infant should weigh about so much, and the number of pounds is one measure of its condition. Its weight should increase at a normal rate, and here the weight becomes an index of nutrition and good health. The measure of body temperature is an advance indicator of illness. Especially in recent scientific studies of childhood is the importance of measurement keenly realized. The response of muscles and nerves-the measure of the so-called time reactions and sense perception-are elements in studying educational methods, especially subnormal cases. It is possible to set certain approximate standards for the normal child and its growth. Measurements are made of the speed, strength, and fatigue of its reactions; of its height, girth, and other dimensions. Muscle measures and strength tests indicate normal growth or the effectiveness of physical training. The ergograph measures endurance, and the chronograph records perceptions and reaction times. The focusing power of the eyes is measured, and with these measurements the optician can perfect the vision by adapting the measured curvature of glass to the measured defect of vision. The correct measures of the body determine the comfort and effectiveness of clothing. Modern industry owes its efficiency largely to careful measurements which control processes, or fix the dimensions, proportions, and properties of products. Accurate parts of machines or accessories make it possible to manufacture the parts separately and assemble them without special hand fitting. Anyone may then order repair parts, knowing that they will fit into the machine. In many industries the measured control of heat, electric current, or power is essential to efficient operation. Bread should rise at a definite temperature, steel should be quenched at a certain stage in cooling to give the best results, and similar account must be taken of many things to secure the desired quality. Properties of materials are measured or tested, and this gives a means of controlling quality. Measurement guides the processes of all industries and keeps their output up to certain standards. Careful determinations of the properties of materials are coming to mean more and more to business and industry, and the determination of properties of standard materials is an ever-increasing part of the work of this Bureau. 3. Measures of Trade and Their Inspection The Bureau of Standards is also active in the phase of measurements that touches the household very directly-the weighing and measuring of goods bought, sold, and transported. Much inaccuracy and fraud exist. Weights and standards and instruments are subject to accident, deterioration, and tampering. For these reasons systematic inspection of trade weights and measures is regarded as a function of the Government. In order that the standards throughout a country should be uniform, the custody of the fundamental standards rests with the National Government, which is authorized to fix the standards of weight and measure. In the United States the actual inspection service, being necessarily local, has been left to the States and cities. This Bureau's work has been (1) to provide the States with standardized sets of weights and measures, (2) to encourage and stimulate intelligent interest in the State and local regulation and inspection of weights and measures, (3) to cooperate with the local sealers regarding the technical details of inspection service, and (4) to gather data regarding the standards and instruments in use. 4. Measurements of Household Products and Processes Improved precision has slowly evolved from the guesswork of earlier times. For example, terms like the "pinch of salt,' "speck of pepper," "handful of rice," "sweeten to taste" (units of vague magnitude) have gradually been replaced by definite amounts specified and measured. A process is uncertain of success unless the effect of all the factors entering into it is known. In factories where food is prepared on a large scale, temperatures are carefully measured or determined automatically, and amounts and times are accurately controlled. These methods, which make for efficiency and economy, are being used more and more in the household. Such measurements as require costly or delicate apparatus can not yet be expected to be common in the home; and some still think that the measurement of temperature of rooms, of ovens and sirups, and the weighing of purchases, etc., are unimportant. However, scales, thermometers, and a few other simple measuring appliances can be obtained for a small expenditure, and this |