THE VALUE OF INSTRUMENTS. 267 



itself. We have been able to perceive the priceless value 

 of some scientific instruments in the foregoing pages. It 

 has become commonplace to say that the invention of an 

 instrument may change the face of a science and give it 

 a new start. Remove the telescope from our scientific 

 development, and at once astronomy is dwarfed into common 

 knowledge : its scientific aspect disappears. Mathematics, 

 it is undeniable, would have done much, and had indeed 

 done much, to elucidate the constitution of the heavens. 

 Copernicus, by means of calculation, empirical observations 

 aiding, arrived at the truth. But his conclusions would have 

 remained a field of controversy, and seemed to many mere 

 speculations, without Galileo's instrument and Tycho Brahe's 

 accurate observations by the use of it : the telescope sub- 

 stantiated his doctrines. The calculations of Kepler were 

 grounded on telescopic data, and would have been valueless 

 without. Newton himself would have been powerless in 

 the absence of the same telescopic revelations. He would 

 have remained a great physicist instead of being the prince 

 of astronomers and mathematicians. The telescope settled 

 the problem irrevocably, and set doubt at defiance. Take 

 away the microscope, and physiology ceases to exist as a 

 science, and not physiology merely but a large number of 

 chemical and physical facts would never have been ascer- 

 tained, or even so much as investigated at all. The prism, 

 simple and unassuming as it seems, was the key to celestial 

 physics, and more, to a vast area of philosophical' solutions. 

 Thermology would .have been not so much as a word> 

 without the thermometer. We' have been able in the course 

 of our rapid survey to gauge, not indeed the whole extent, 

 but at least the main bulk of the services rendered by 

 instruments. As we owe the knowledge of our planet's 

 size and configuration, geography, to the compass; so we 

 owe to the pendulum and the barometer our mastery of 

 barology and meteorology ; to magnifying glasses our 

 mastery of optics ; to the balance mainly, our mastery of 

 chemistry ; to the camera obscura, photography ; to the 

 battery, our mastery of electricity and a wide range of 

 phenomena. How mathematics, which are a means to an 



