His family roots were French, so his name was probably pronounced LeCONT...with no final "e." But there are some other names in the Sierra that can be confusing as well.
We've been listening to an interesting series of lectures on Victorian England, and one of the lectures has been about the key scientists of the age, including Charles Lyell, after whom a few features in Yosemite are named--like the Canyon, the mountain, and the Lyell fork of the Tuolumne River. But we were surprised to learn that he pronounced his name Li-YELL, with a clear accent on the second syllable.
We've always pronounced it, and heard it pronounced as if it were a cotton: Lisle.
Now you know. It's Ly-YELL. And he was Scottish.