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Rh telescopes. They were made with mirrors—reflecting telescopes, as they are called—and they ceased to be so very thin. Indeed, on the contrary, they became quite fat, for there is a great advantage in having the mirror as wide as possible:

you can see much more clearly with a wide telescope than with a narrow one, always assuming that the wide one is just as well made. But it is much harder to make a big wide mirror than a little one, just as it is harder to get 100 runs at cricket than to get ten; the batsman may play several overs successfully, but he has to be terribly careful not to make a mistake if he