By this he means that because of how he wanted other people to view him, he divided his nature more than he says most people do. A"province"is an area of land under a particular jurisdiction, like a county or country. Jekyll uses the word to continue the geographicalmetaphorthat begins with a"deeper trench. The image is visual - instead of the abstract aspects of good and evil within a person's mind or soul, we are asked to imagine a landscape split by a vast trench.The good and ill"divide and compound"man's nature means that they both split it but also make it complete: Stevenson suggests that we are a compound - an integrated mix - of both good and bad, neither wholly one nor the other. What Jekyll has done in dividing them totally is therefore unnatural.