"Yet the evil still increased, and, like the parasite of barnacles on a ship, if it did not destroy the structure, it obstructed its fair, comfortable progress in the path of life"

This quote by William Banting is a metaphor comparing evil to a parasite of barnacles on a ship. The barnacles are an annoyance to the ship, as they attach themselves to the hull and slow down the ship's development. Likewise, evil can attach itself to a person's life and hamper their development. The metaphor recommends that evil can be challenging to eliminate, as barnacles are difficult to get rid of from a ship's hull. The quote suggests that evil can be relentless and difficult to get rid of, and can cause an individual to have a hard time to make development in life. It is a suggestion that evil can be a limitation to an individual's development, and that it is necessary to be familiar with its presence and take actions to remove it.