THE YERKES 4O-INCH REFRACTOR 



(The largest refracting telescope in the world. Its big lens weighs 1,000 

 pounds, and its mammoth tube, which is 62 feet long, weighs about 12,000 

 pounds. The parts to be moved weigh approximately 22 tons. 



The great loo-inch reflector of the Mount Wilson reflecting telescope 

 the largest reflecting instrument in the world weighs nearly 9,000 pounds 

 and the moving parts of the telescope weigh about 100 tons. 



The new 72-inch reflector at the Dominion Astrophysical Observatory, 

 near Victoria, B. C. , weighs nearly 4,500 pounds, and the moving parts 

 about 35 tons.) 



