Every Day Science for Boy 2 Mechanics e PES 11 liT Grant 31 M. Hyde Wh Why Is Js It It Daddy that all these advertisements advertisements advertisements ad ad- of ot this automobile aro are alike aliko In all the tho newspapers newspapers exactly exactly the tho samo pictures picture and printing printing printing-as as If they thoy were vero all printed at nt tho the same time Because the they are printed from electrotypes elec I supplied to lO tho the newspapers by bytho I the tho advertisers I told you OU about stereotyping store stere I tho tho reproducing o of typo type mattor mattor mat mat- I tor ter b by hy means menns of or a n wet macho papier-macho ml mat t later inter baked hard to form a mold for Cor casting a loud lead plate i Is a finer and more moro costly process for doing tho the samo thing Although vcr very ory I useful for Cor somo purposes stereotypes I L i 5 i pt caNt s' s jy- jy are aro soft soon wear out and ana do not make a perfect Impression Electrotypes Electrotypes Electro Electro- types typos are nrc better because they thoy have hn a copper surface which wears Wei longer and prints better beller Such plates aro ao made mado b by electrolysis sis sis th the process you ou learned learnell About In school whereby an nn object is plated with witha a n metal by means of or electric current passing passin through h a a. liquid containing salta of or tho the metal An n electrotype la is mado matIe by plating with wa wax sax In Itt the tho process a sheet of at wax is 18 pressed over I the tile typo type form and ancl thus rc receives an impression which mat mav be he coated with und chemicals to make malo It an electric conductor Then tho the wa wax l in hI suspended In a tank of or copper and I plated copper IJ by means mean of oC electric current Tho thin film of ot copper that thatIs Is 15 deposited on Its surface Is later laler peeled off otC like a paper skin containing a reproduction of or the tho type hpe When Whon molten tin anti and lead lend have havo been poured on this film and hardened d tho the result is a plated copper reproduction of oC tho the original type tYre Electrotypes or electros ore arc s sent nL by many advertisers to newspapers and magazines as 18 a cheap wa way to 11 have havo all nIl their ad advertisements look alike Klec- Klec are also us used usell oil In book and antI mn magazine offices because they are arc light and arid cas easy to store storo and because In a magazine of ot largo large c circulation typo lype would wear out before all 11 of or tho edition edi lion tion was waa printed Next ext week Makin Making g Artificial Ice Copyright 1920 h by J. J II Millar I