266 A SHORT HISTORY OF SCIENCE 



Every student should read the earlier parts of Newton's Optics in 

 which are described the fundamental experiments on the decomposi- 

 tion of white light. LORD RAYLEIGH. 



The work of Christian Huygens, towards the end of the seven- 

 teenth century, second only to that of Newton, both hi extent and 

 importance, touched upon a great variety of subjects, including 

 some in the natural sciences. As a young man he wrote upon 

 geometry ; in early middle life he invented the cycloidal pendu- 

 lum. He was the first to apply pendulums to clocks and spiral 

 springs to watches, and to devise the achromatic eye-piece which 

 still bears his name. He also made a telescope and, finally, at 

 the age of fifty, observed the phenomena of polarization and, 

 most important of all, proposed the modern wave theory of light. 



THE FIRST SCIENTIFIC INSTRUMENTS: TELESCOPE, BAROM- 

 ETER, THERMOMETER, AIR- PUMP, MICROSCOPE, MANOMETER. 

 The complete history of the origin of the telescope, the ther- 

 mometer and the microscope is not known. The account usually 

 given of the invention of the telescope makes it accidental and 

 due to the children of a Dutch spectacle maker, named Jan sen, 

 who while at play happened to bring together two lenses in such 

 a way that a distant church spire seen through them looked mag- 

 nified and near. The father, whose attention was drawn to the 

 phenomenon, seeing in the arrangement a source of profit, there- 

 upon made and sold the combination as a toy or "wonder," under 

 , which form it was on sale in 1609, becoming known to Galileo, who 

 instantly realized its importance and made improvements in it. It 

 appears that soon after 1609 Galileo had a fairly good instrument, 

 magnifying 8 diameters, with which he was quickly and easily 

 able to make some of his most splendid astronomical discoveries. 



The early history of the telescope shows that the effect of com- 

 bining two lenses was understood by scientists long before any partic- 

 ular use was made of this knowledge; and that those who are 

 accredited with introducing perspective glasses to the public hit by 

 accident upon the invention. Priority was claimed by two firms of 

 spectacle-makers in Middelburg, Holland, namely Zacharias, miscalled 



