Answer:
Principles of Geology
Explanation:
J. Henslow gifted Darwin the first volume of Principles of Geology, written by Charles Lyell. The book explains about the old age of the earth. Accordingly, the slow rate of several geological processes suggests that the earth is very old.
Darwin read the book as the ship was crossing the Atlantic and learned about geological processes occurring over the millions of years. For example, he learned that the earth's surface was not formed by some catastrophic event.
In his book, Lyell explained the slow and gradual geological processes like erosion gave rise to the vast landscapes present on the earth's surface.
Darwin compared the time taken by geological processes to form the earth's surface and reasoned if these millions of years were enough to support the evolution of species.
<h2>Operational </h2>
Explanation:
The operational definition is the description of a specific process, or set of validation tests, accessible to more persons than the definer (i.e., said to be publicly accessible), where it can be repeatedly measured or tested
Operational definitions are also used to define system states or (nonspecific) physical objects by the description of a specific process of preparation which can be repeated
For example in the given example experimenter is using the case of hitting a punching bag to measure the level of aggression in someone