204 The Smithsonian Institution 



good for a boy. One of the most wonderful things to me 

 / was the sun, and as to how it heated the earth. I used to 

 hold my hands up to it and wonder how the rays made them 

 warm, and where the heat came from and how. I asked 

 many questions, but I could get no satisfactory replies, and 

 some of these childish questions have occupied many years 

 of my later life in answering. I remember, for instance, one 

 of the wonders to me was a common hotbed. I could not 

 see how the glass kept it warm while all around was cold, 

 and when I asked, I was told that ' of course ' the glass kept 

 in the heat ; but though my elders saw no difficulty about it, 

 I could not see why, if the heat went in through the glass, it 

 could not come out again. Since then I have spent many 

 years in studying the way that that great hotbed, the earth 

 itself on which we live, is, by a like principle, made warmer 

 by the atmosphere that covers it." 



Professor John W. Langley, of the Case School of Applied 

 Sciences in Cleveland, writes in response to a recent letter 

 of inquiry : 



" My brother quite early in life showed a marked fondness 

 for astronomy. I remember that when he was about twenty 

 years old he used to make small telescopes. In this work I 

 used to help him, and being his junior in years, my position 

 was that of first assistant. 



" With these early telescopes it was possible to see Jupi- 

 ter's moons, and the phases of Venus ; Saturn appeared as 

 an elliptical object with a faint indication of a separation 

 between the planet and its ring. 



"Somewhat later, in the autumn of 1864, we had about 

 three months in which both of us were free from fixed duties, 

 and we decided to build a reflecting telescope. My brother 

 and I had made the acquaintance of Alvan Clark, Sr., who 

 at that time was a portrait painter. He had a studio in 

 Tremont Street, Boston, but he was just abandoning art for 

 optics, and his studio contained about as many lenses in an 

 unfinished state as it did portraits, also incomplete. At this 



