Up to 1939, agates and large pieces of rough stone were still worked in mills which dot the sides of the winding river Nahe. The flowing water is diverted near the mill to form a pond, and by a system of sluices, it is controlled to fall on to a large flanged wheel. This mill wheel is thus revolved by the power of the water, and another system of pulleys and belts from the wheel transmits the power to the cutting and grinding stones within the mill itself. The water is then directed back to its normal course, where it joins the main stream on its downward path. A number of stone cutting mills which border the river at intervals are thus served by the same water.
The mills are run on a co-operative system, one man being elected the foreman by the workers, who might number up to ten. The foreman deals with the merchants, who give him a certain weight of rough stone with directions as to what they require to be cut. Payment of the work is shared out on a prearranged basis, the cut stones being returned to the merchant when ready. In a few instances, it has occurred that some of the rough stone not used has been retained by the workers, with the result that cut stones at a cheap price find their way on to the market, thus leading to undercutting. The men work together and buy their own equipment, such as wheels, laps, and belts, and also rent the small hut and often a piece of adjoining ground. If necessary, they can easily get an advance from a merchant or a bank for the purchase of necessary materials. Slitting, grinding, polishing, and drilling are all separate and different operations, sometimes being carried out by different mills. Drilling is always done by one who specializes in this craft, often at home in one room set aside as a workshop.