There's never any empirical evidence of causality.

(And certainly not any empyrical evidence (what does causality have to do with coal?.) ;)

Hume was the one who best demonstrated why this is the case:

"Being an empiricist, Hume argued that all causal knowledge stems from experience. He revolted against the traditional view that the necessity that links cause and effect is the same as the logical necessity of a demonstrative argument. He argued that there can be no a priori demonstration of any causal connection, since the cause can be conceived without its effect and conversely.

His far-reaching observation was that the alleged necessity of causal connection cannot be proved empirically either. As he famously argued, any attempt to show, based on experience, that a regularity that has held in the past will or must continue to hold in the future will be circular and question-begging. It will presuppose a principle of uniformity of nature. But this principle is not a priori true. Nor can it be proved empirically without circularity.

For any attempt to prove it empirically will have to assume what needs to be provednamely, that since nature has been uniform in the past it will or must continue to be uniform in the future. This Humean challenge to any attempt to establish the necessity of causal connections on empirical grounds has become known as his skepticism about induction. "

[http://science.jrank.org/pages/8538/Causality-Hume.html]