Gravis and Ferris first decided to go to a Law Comprehension Area regarding wind. This wasn't a Law Comprehension Area for the powerful kind of wind that was the equivalent of Punishment Lightning. This was a Law Comprehension Area for all different kinds of Wind Laws.
Gravis' goal in coming here was to understand the Composition of Wind and Air. With his new knowledge about the difference between the wood element and bark, Gravis had already anticipated that the Composition of Air was probably a different Law to the Composition of Wind. Wind was an element, while air was a material.
Yet, by now, Gravis wasn't sure anymore if he actually needed to understand the Composition Law of Wind to get the Middle-Tier Material Composition Law. There was a high possibility that he only needed to understand the specific materials instead of the elements. Maybe the elements were part of the Middle-Tier Composition Law, without the "Material" word.