vi List of Portraits 



JAMES PEESCOTT JOULE - Facing p. 160 



From a photograph by Lady Roscoe. 



WILLIAM THOMSON, LORD KELVIN - Facing p. 190 



From a photograph by Messrs. Dickinsons. 



THOMAS YOUNG - - Facing p. 212 



From a portrait by Sir Thomas Lawrence. 



JOHN RAY - - Facing p. 232 



After a portrait in the British Museum. 



STEPHEN HALES - - Facing p. 236 



After a portrait by Thomas Hudson. 



CHARLES DARWIN - Facing p. 268 



After a photograph by Messrs. Maidl & Fox. 



WILLIAM HARVEY - Facing p. 294 



After a painting by Cornelius Janssen, now at the College of 

 Physicians. 



CHARLES LYELL - - Facing p. 310 



After a daguerreotype by J. E. Mayal. 



