PREFACE v 



earlier text was written primarily for use in the Illinois State 

 Normal University and was the outgrowth of a course which 

 had already been taught for several years. At that time no 

 similar material was available; the demand for general science 

 in the high school had not yet risen. The earlier book was 

 prepared with the definite purpose of getting away from the 

 abstract and impractical science of the day. It is the belief 

 of the authors of this text that the present strong demand for 

 general science in the high school is a demand for the accom- 

 plishment of the same end. 



We wish to express our appreciation of the painstaking and 

 efficient reading of proof by Laura Hayes Pricer. We also 

 appreciate highly the aid rendered by those who have assisted 

 in the preparation of the illustrations or who have granted us 

 permission to use illustrations from their publications.* The 



* In the preparation of the illustrations for this text the authors wish to 

 acknowledge valuable assistance from the following sources. Some of these 

 illustrations appear unmodified; some have been adapted to the special needs 

 of a text- book; some have been prepared especially for this text. 



The Century Company, Figs. 2, 64, 86, 352, 355, 361. Detroit Heating 

 & Lighting Company, Figs. 19, 20. J. B. Colt & Co., Figs. 31, 32. 

 Prestolite Company, Fig. 34. Westinghouse, Church, Kerr & Co., Figs. 

 41, 42. American Home Magazine Co., Figs. 43, 44, 45. General Electric 

 Co., Figs. 46, 47. Central Electric Co., Figs. 37, 38, 50, 52, 53, 54. Welsbach 

 Company, Figs. 56, 57, 58, 59, 60, 61. Curtis Publishing Co., Fig. 65. Kala- 

 mazoo Stove Co., Figs. 73, 114. Patric Furnace Co., Figs. 74, 75. William- 

 son Heating & Ventilating Co., Figs. 76, 77, 78, 92, 93, 94. American 

 Radiator Co., Figs. 103, 233, 234, 237. Edwin J. Jackson & Bro., Figs. 

 104, 105, 106. Durham Manufacturing Co., Fig. 116. Mechanical Refrig- 

 erator Co., Fig. 123. Encyclopedia Americana, Fig. 127. Monthly Weather 

 Review, Figs. 192, 193 and others. Dr. S. Adolphus Knopf and M off at, 

 Yard & Co., Figs. 228, 229, 230. Waterbury- Waterman Co., Figs. 235, 

 236. Municipal Magazine, Fig. 242. Standard Sanitary Manufacturing 

 Co., Figs. 277, 297, 298, 311, 312. R. D. Wood & Co., Figs. 295, 301, 372, 

 373. Bishop & Babcock Company, Jig. 300. Rensselaer Manufacturing 

 Co., Fig. 302. Thompson Meter Co., Fig. 304. National Meter Co., Figs. 

 305, 306. F. J. Drake & Co., Fig. 316. Chas. Brossman, Indianapolis, Figs. 

 317, 318, 319, 320, 321. International Harvester Co., Figs. 322, 364, 366, 

 368, 370. Singer Sewing Machine Co., Figs. 323, 324, 325, 326, 327, 328, 

 329. Mississippi Power Co., Figs. 345, 346, 349, 351. DeLaval Manufac- 

 turing Co., Figs. 331, 332, 333. American Book Co., Fig. 353. James Leffel 

 & Co., Figs. 358, 359, 360. Westinghouse Manufacturing Co., Figs. 62, 63. 

 Parrett Tractor Co., Fig. 339. Swift & Co., 252, 253, 254. Creamery 

 Package Co., 251. U. S. Weather Bureau, Figs. 147, 148, 154, 155, 166, 172, 

 173, 174, 175, 176, 177, 178, 189, 190. Perfection Vacuum Cleaner Co., 

 Fig. 241. 



