'Ultraviolet light,' I yawned, remembering something I had read in a magazine about it.

Billy wiggled his ears and went on: 'Most likely ultraviolet has a lot to do with it. The spots themselves aren't strong emission centers for ultraviolet. But it may be the very changes in the Sun's atmosphere which produce the spots also result in the production of more ultraviolet.

'Most of the ultraviolet reaching Earth's atmosphere is used up converting oxygen into ozone, but changes of as much as twenty percent in its intensity are possible at the surface.

'And ultraviolet produces definite reaction in human glands, largely in the endocrine glands.'

'I don't believe a damn word of it,' Herb declared flatly, but there was no stopping Billy.

He clinched his argument: 'Let's say, then, that changes in sunshine, such as occur during sunspot periods, affect the physiological character and mental outlook of all the people on Earth. In other words, human behavior corresponds to sunspot cycles.

'Compare Dow Jones averages with sunspots and you will find they show a marked sympathy with the cycles – the market rising with sunspot activity. Sunspots were riding high in 1928 and 1929. In the autumn of 1929 there was an abrupt break in sunspot activity and the market crashed. It hit bedrock in 1932 and 1933, and so did the sunspots. Wall Street follows the sunspot cycle.'

'Keep those old sunspots rolling,' I jeered at him, 'and we'll have everlasting prosperity. We'll simply wallow in wealth.'

'Sure,' said Herb, 'and the damn fools will keep jumping off the buildings.'

'But what would happen if we reversed things – made a law against sunspots?' I asked.

'Why, then,' said Billy, solemn as an owl, 'we'd have terrible depressions.'

I got up and walked away from him. I had got to thinking about what I had seen on the sidewalk after the fellow jumped, and I needed that beer.