DIELECTRIC 



1795 



DIFFRACTION 



Die Sinking. The making of dies, called die 

 sinking, is an industry requiring great skill. 

 The die sinker first makes a pencil tracing of 

 the design he is to reproduce. The surface of 

 the metal employed is coated with white paste, 

 on which the tracing of the design is pressed. 

 Gentle rubbing of the back of the tracing 

 causes the lines to be transferred to the surface 

 of the metal. The lines are then cut to the 

 required depth with sharp steel tools. From 

 the original die, which is hardened and tem- 

 pered, any number of copies may be made by 

 stamping or punching in a softer metal, which 

 is then hardened for use. 



DIELECTRIC, dielek'trik, the name gen- 

 erally given a non-conductor of electricity, such 

 as the glass between the outside and inside 

 coating of a Leyden jar (which see). In other 

 words, a dielectric is an insulator; the term is 

 particularly applied to a non-conductor placed 

 between two good conductors of electricity. 

 In the practical use of electricity mica and 

 paraffin paper are extensively used as non- 

 conductors. See ELECTRICITY; INSULATOR. 



DI'ET. This word is derived through the 

 French and Latin languages from the Greek 

 diaita, which means manner of living. In the 

 English language, however, the meaning is con- 

 fined to one item of the manner of living, 

 namely, the food. The food which one takes 

 regularly is one's diet. Very often a person 

 suffering from disease is "put on a diet"; that 

 is to say, the physician prescribes the nature 

 of the foods to be taken, and sometimes the 

 quantities of each. Soldiers and sailors are 

 issued a certain ration, that is, allowance of 

 foods. If a soldier uses his whole ration, that 

 ration constitutes his diet. The diet of a 

 healthy person must be such as to maintain 

 the health. It must contain sufficient of the 

 proteins to make good the waste of protein 

 that is inseparable from the life-processes of 

 the body. It must also contain sufficient fuel 

 material to maintain the body temperature 

 and to provide energy for all the motions of 

 the body. It must include sufficient water to 

 make up for the water eliminated from the 

 body through the lungs, skin and kidneys; and, 

 finally, it must contain sufficient of each of the 

 minor constituents of foods for its peculiar 

 functions. 



Under the title FOOD in these volumes will be 

 found a classification of the substances found 

 in foods and a table showing the composition 

 and fuel value of some common foods. In 

 the same article the influences of sex, age, 



occupation and climate upon the food require- 

 ments are discussed. The following is an esti- 

 mate of the daily food requirements of a man 

 of average weight (150 pounds) doing an aver- 

 age amount of work: 



Proteins, four ounces ; fats, three ounces ; car- 

 bohydrates (sugars and starches), fourteen 

 ounces ; water, four quarts. 



Such a diet would have a fuel value of 2,850 

 calories (see CALORIE). These requirements 

 would be met by the following selection of 

 foods (but it must be borne in mind that many 

 other combinations of foods could be made 

 which would also conform to the same stand- 

 ard) : 



One pound bread, one-half ounce butter, three- 

 ounces oatmeal (dry weight), one and one-half 

 pints milk, four ounces roast beef and two 

 ounces sugar. 



In armies and navies, and in prisons, hospi- 

 tals for the insane and other institutions where 

 large numbers of people have to be fed reg- 

 ularly, the dietary has to be carefully worked 

 out so as to provide enough food for each per- 

 son and enough of each food substance, and at 

 the same time to keep the cost as low as pos- 

 sible. The branch of hygiene and medicine 

 which treats of diets in their relation to health 

 and disease is called dietetics. J.F.S. 



Related Subjects. The reader Is referred to 

 the following articles in these volumes : 



Carbohydrates 



Digestion 



Fats 



Food 

 Protein 



DIET, the name applied to the Hungarian 

 Parliament and to the legislative assemblies of 

 German states and Austrian provinces. In the 

 days of the Holy Roman Empire the name was 

 given to the imperial Parliament. The word 

 also refers to a formal public assembly, pop- 

 ularly applied in Europe for many years to 

 religious assemblies for special purposes. In 

 1521 Martin Luther was brought before the 

 Diet of Worms for inquiry into what were con- 

 sidered his heretical views. 



DIFFRACTION, dif frak ' *hun. If the edges 

 of two knife blades are placed together and 

 held up to the light one can see rainbow tints 

 through them. If a small round hole is made 

 in the shutter to a dark room and the rays 

 of light forcing through it are allowed to fall 

 on a screen, an image of the sun surrounded by 

 rainbow tints will be seen. A slit in a window 

 shade will produce a similar effect. This play 

 of colors is also seen in the mother-of-pearl 



