COLUMBUS, OHIO, November 7, 1869. MY DEAR WEBB: Yesterday one of the teachers in the public schools tried an interesting experiment in the...

Mr. Alvan Clark, of Cambridge, Massachusetts, has constructed an achromatic telescope, said to be the largest in the world.   The glass has...

(From the N. Y. Scientific American, April 5.) MESSRS. EDITORS:– In your issue dated Saturday, March 29 th , you asked the question, “what ...