They're talking about The Sense of Wonder over at the Rachel Carson Centennial Blog.
I have two copies of The Sense of Wonder. One I bought some years ago for my personal collection while the second, the older of the two but newer on my bookshelf, was gifted to me by a friend. A naturalist and infamous collector, he makes it a point to seek out and buy every copy he can find of the older 1965 edition for one key reason: it has more pictures of kids.
Check it out here.