226 PROGRESS OF SCIENCE. 



our electric light. But this was the work of Humphrey- 

 Davy, as we stated in our chemical section. Thus was 

 Volta's invention of the battery the STARTING-POINT OF 

 A REVOLUTION IN SCIENCE, and of a succession of dis- 

 coveries in the XlXth century which are unparalleled in 

 the history of mankind. WATT AND VOLTA were the two 

 men who will be known to posterity as the originators of 

 the TWO GREATEST AGENTS OF CIVILISATION next to 

 printing the steam-engine and electric pile. Besides the 

 telegraph, electric light, the telephone, and a thousand 

 other applications, industry, chemistry, medicine, and other 

 sciences owe immeasurable progress to the voltaic battery. 



1749 1827. Laplace, so great as a mathematician and 

 astronomer, was also great as A PHYSICIST. He invented 

 with Lavoisier the ICE-CALORIMETER ; he demonstrated the 

 statical PROPERTIES OF ELECTRICITY, and showed the force 

 to act like gravitation, that is, in the inverse ratio of the 

 square of distances ; made numerous valuable observations 

 on refraction, capillarity, barometrical measurements, pre- 

 pared for future extension the application of mechanics to 

 corpuscular physics, by demonstrating that the molecular 

 compositions of material bodies present so many new worlds, 

 subjected to the laws of mechanics, which science has to 

 investigate; and the science of our day has already shown 

 that his expectations in that respect were well founded. 



1753 1814. Rumford, before Arago, Bunsen, and 

 Wheatstone, invented a PHOTOMETER for measuring the 

 relative intensities of light; he also invented a CALORIMETER 

 which bears his name ; he made numerous observations on 

 heat and light which received practical applications for 

 domestic purposes being the first to use steam for cooking 

 and warming. He showed that the quantity of light is in 

 proportion to the vivacity of combustion, and not to the 

 quantity of the matter burnt; likewise that intensity of heat 

 depends on the intensity of the draught, and not on the 

 quantity of fuel. Housekeepers would find many of his 

 suggestions conducing to economy. He showed ex- 

 perimentally the conductivity of steam, air, and the 

 transparency of a flame. He was, too, the first to de- 



