On This Day: Astronomer Angelo Secchi demonstrates the Secchi disk, which measures water... (1865)

On April 20, 1865: Astronomer Angelo Secchi demonstrates the Secchi disk, which measures water clarity, aboard Pope Pius IX's yacht, the L'Immaculata Concezion.

This historical event can serve as a powerful sermon illustration about how God works through the events of history. Consider using it when preaching about history.