“All right, explain.”
The boy looked up at him. He was a city boy and used to the streets. Here was some old high-brow challenging his wisdom. Of course he knew. “It’s the sun.”
“There,” laughed the man. “Of course. You said you knew, but you don’t. Why doesn’t the sun, without the glass, burn the paper? Tell me that.”
The boy was still looking up at him; he saw that the man was not like the others on the street. It may be that the strange intimacy kindled into being at that moment. Certainly it was a strange unbending for the doctor.
“It would if it was hot enough or you could get enough of it together.”
“Ah! Then that is what the glass is for, is it?”
“Yessir.”
“Concentration?”
“Con— I don’t know, sir. But it’s the sun. She’s sure some hot. I know a lot about the sun, sir. I’ve studied it with the glass. The glass picks up all the rays and puts them in one hole and that’s what burns the paper.
“It’s lots of fun. I’d like to have a bigger one; but it’s all I’ve got. Why, do you know, if I had a glass big enough and a place to stand, I’d burn up the earth?”