n8 GREAT MEN OF SCIENCE 



in 1714); cared for only by his secretary, he died at the age of 

 70, a lonely man. Not until fifty years after his death was his 

 grave in the Court Church at Hanover made recognisable 

 by a suitable inscription. 



Leibniz is described as of middle height, stooping some- 

 what, with broad shoulders but spare of build. His hair 

 was very dark. 



Leibniz's many travels, his relationship to the princes, 

 his great versatility, and his extensive correspondence, gave 

 him great influence in the scientific life of his time. He 

 became in 1700 founder of the Berlin Academy. His corre- 

 spondence, particularly with Papin, shows him concerned 

 in many directions with inventions which only later became 

 practicable, as for example the proposal to make a barometer 

 without mercury, consisting of a flexible closed vessel with a 

 vacuum inside and held by a spring in equilibrium with the 

 atmospheric pressure; the aneroid barometer of the present 

 day. He was also concerned with the steam engine, as the 

 following facts go to show. 



Dionysius Papin, the first to conceive a steam engine with 

 a cylinder and piston, and to construct one, was born in 

 Blois (south of Paris), and studied medicine. At the age of 

 twenty-four he went to Paris, where he made the acquaint- 

 ance of Huygens, to whom he attached himself; and this 

 brought him also in contact with Leibniz, with whom he 

 continued to exchange ideas by a correspondence which at 

 times was very active.^ Huygens at that time was busy with 

 air-pump experiments (he also introduced in the course of 

 them the flat plate with the convenient bell receiver set 

 upon it, which has always since been retained), whereby 

 Papin proved a very gifted and skilful experimenter. The 

 work of Guericke which had just appeared concerning the 



^ See Leibniz's and Huygens' correspondence with Papin (edited by 

 E. Gerland, Berlin, 1881). 



