At Paris, just after dark one gusty evening in the autumn of 18—, I was enjoying the twofold luxury of meditation and a meerschaum, in company with my friend C. Auguste Dupin […]. For one hour at least we had maintained a profound silence; while each, to any casual observer, might have seemed intently and exclusively occupied with the curling eddies of smoke that oppressed the atmosphere of the chamber. (1)
Not the most exciting beginning, but who isn't charmed by this image of two hyper-cerebral young men sitting back and watching the smoke-patterns in the dark? All the while they are thinking, thinking, thinking, stimulated by what we assume is tobacco smoke, and the images it creates against the darkness. The rhythm of the "curling eddies" is like the rhythm of their thoughts—free floating, but focused.
This symbol suggests that imagination is an important part of analytical thinking. After all, Dupin's major complaint is that G— lacks imagination and (literally) vision. For Dupin and the narrator, reality is different than it is for G—.
The image the passage produces is one of outline, shadow, and smoke. Since the room is dark, we can only imagine dim outlines, shadow figures, and drifting smoke—again, kind of an image of thought itself. Dupin uses the mysterious process of thought to solve mysteries—you might even say to clear the smoke. How ironic.
Also, rather Gothic. Notice that the narrator says the smoke "oppressed" (to oppress is to "crush" or "burden") the "atmosphere." While this is far less oppressive than Poe's usual parade of live burials and other entombments, it still has that Gothic feel—check out "Genre" for more. (Especially when we think about what the insides of their lungs look like.)
A fun little fact about this symbol: because of Arthur Conan Doyle's Dupin-inspired Sherlock Holmes) stories, the pipe is a symbol of detection. So, we can blame both authors for glamorizing smoking. That said, click here for the fascinating history of Meerschaum pipes (emphatically for educational purposes only!).