Hello. You did not present the text to which this question refers, which makes it impossible for this question to be answered. However, I will try to help you in the best possible way.
To answer this question you will need to read the entire article. However, you will be able to identify the phrase that helps explain why prospectors must start each morning in search of a spring, by the phrase that presents a reason, a circumstance, or a result that they sought to achieve in doing so.
