All of his speeches are available for free on the internet. I’ve included links below.
How the God’s Grow
Robert Ingersoll (1833 – 1899) was an American lawyer, a Civil War veteran, political leader, and orator of the United States during the Golden Age of Free Thought, noted for his broad range of culture and his brilliant defense of agnosticism. He was nicknamed "The Great Agnostic".
Ingersoll was known for his passionate and articulate speeches that were often delivered in packed auditoriums across the US to rapt audiences. The following is one of short speeches called “How the God’s Grow”.