doubtedly excellent observations he was too hasty in what he then wrote, and too rash in the conclusions he then drew. But let it be recorded to his honour that to him belongs the credit of first sending the beams of Sirius and other sunny stars through a prism, for the purpose of determining whether their light is like our sun's or not. It was a most brilliant idea, carried out before the world was ready to receive it.
The great question Herschel set himself to solve regarding the sun was, What is it? He knew, as all men had known, that it was a vast fiery ball ruling earth and sky; but he saw, as they saw, nothing save the outside of the ball. Was it a mighty furnace within as it was without? In Newton's days, two or three generations earlier, there were people who "supposed the sun to be cold," although Newton easily showed that, to "a body hard by the sun, his heat would be 50,000 times greater than we feel it in a hot summer day, which is vastly greater than any heat we know on earth."[1] Herschel was aware that the spots, the black spots on its face, were vast dark holes in its white brightness, so large that they would let the earth dive in, and be at a thousand miles' distance all round from the burning, blazing clouds. But while he knew this, he had also learned from the writings of others that these black rifts were careering over its face from west to east at the rate of more than a mile every second. What did it all mean, was the question he wished answered. Fabricius in 1611, and Galileo about the same time, divide between them the honour of discovering these spots on the sun's face. The former tells the story of his first sight of a spot, of his
- ↑ Brewster, Life, ii. 455.
