Final answer:
The provided texts do not specify the exact number of vessels approved for purchase by the Second Continental Congress; thus, an accurate response based on this information is not available.
Step-by-step explanation:
The Second Continental Congress was engaged in critical efforts to fortify the American colonies following conflicts in Massachusetts, such as the clashes at Lexington and Concord. As tensions with Britain escalated, it became apparent that military preparations were necessary. In response, the Second Continental Congress approved funds for various military expenses, including the formation of the Continental Army, led by George Washington. However, there are no specific references in the provided texts indicating the exact number of vessels approved for purchase by the Second Continental Congress. Therefore, based on the information given, an exact answer regarding the number of vessels cannot be provided. For a definitive answer, further research or a different source would be required to find out how many vessels were authorized for purchase by the Second Continental Congress.