Let's see, the wooden chamber is filled with tobacco, then smoked,during the smoking process tars, nicotine and moisture comes out of the tobacco. Since the chamber of burning tobacco is above the Meershaum chamber the tars, nicotine and moisture drops into the Meershaum bowl. The Meershaum bowl absorbs the afore mentioned. Overtime the Meershaum bowl will change color with the coloring bowl the coloring occurs faster and richer. The main difference is just smoking the Meershaum carbon deposits will build on the walls which inhibits the absorption of the afore mentioned. Now with the separate bowl the carbon builds on its walls, the aforementioned items drop into the lower Meershaum.
Now its time to find Mr. Holmes or the good Dr. Watson. Or just another pipe for a smoke.