What is the author's style in The Exploration of the Colorado River and Its Canyons by John Wesley Powell?

he men explored and kept records of the area as they gave names to canyons, gorges and water flows on the three-month expedition. The author returned to the area the following year to explore and chart on land. This completed the charting of unmapped areas in the Untied States. The use of the first person point of view is very appropriate for the kind of book. Ever though it takes a scientific approach, the author is still relating his experiences.