1) Difficulties moving through an unknown country;
"The difficulty was that the country in which he found himself was so featureless--or rather, that it was crowded with features, all exactly alike."
2) heat
3) "His steamer was wrecked and sunk in the Galveston harbour, and he had lost all his worldly possessions except his books, which he saved at the risk of his life. He crossed Texas with a traders'caravan, and approaching San Antonio he was hurt in jumping from an overturning wagon, and had to lie for three months in the crowded house of a poor Irish family, waiting for his injured leg to get strong."
Upon his arrival;
"The Mexican priests there had refused to recognize his authority."
His credentials had not arrived and were questioned.
There are numerous things to include here. Do you have your text?