LIST OF ILLUSTRATIONS 



PROFESSOR MARCELLIN BERTHELOT. Founder of Syn- 

 thetic Chemistry, in his laboratory at the College 

 de France, Paris Frontispiece 



HERO'S STEAM-TURBINE. Earliest-known steam-engine, 



invented about 130 B.C page 12 



HERO'S MAGICAL ALTAR. When a fire was built upon 



the altar, the doors of the temple swung open . page 14 



ARCHIMEDES. Greatest inventive genius of antiquity, 

 born at Syracuse, 287 B.C.; killed by a Roman 

 soldier, 212 B.C facing p. 16 



PROFESSOR SAMUEL PIERREPONT LANGLEY. Secretary 

 of the Smithsonian Institution at Washington, 

 inventor of the bolometer facing p. 50 



PROFESSOR W. C. RONTGEN. University of Munich, 



discoverer of the X-rays facing p. 80 



LORD KELVIN (SiR WILLIAM THOMSON). Famous for his 

 researches in electricity and the constitution of 

 matter facing p. 118 



SIR WILLIAM CROOKES. Chemist and philosopher, dis- 

 tinguished for his work in the field of molecular 

 physics facing p. 138 



PROFESSOR J. J. THOMSON. Discoverer of the ultra- 

 >mic state of matter, in the Cavendish Physical 

 Laboratory, Cambridge, England . . . facing p. 164 

 xi 



