However, a water system so constrained by the slope did not allow the construction of other mills on the same aqueduct. To obviate this and to meet the greater demands of ground in the following centuries, works were carried out to increase the aqueduct flow as other towers and milling systems had been added to the existing mills. In this way every mill could increase its production capacity.
More than three centuries had passed since the construction of the first mills of the 13th century and the technical know-how improved considerably. The grind systems were lighter and with the use of different materials the frictions were significantly reduced, so there was no need for a strong pressure against the wheel. This allowed the construction of smaller Towers that obviously had smaller amounts of water.
Industrial Ecology
The first concessions for the "molendinum in flumine Graniani" are from 1266 and 1272. The construction of the mills and the aqueduct involved a careful study of the path to be achieved, of the total slope and in the various sections. The water system of the Valley provided that the water leaving the base of the single mill was included in the aqueduct, to get to the top of the tower of the next mill. This explains why the distance between the various mills is not uniform but depending on the slope of the land on which they were built. In fact, of the 12 mills left over and distributed over the entire course of more than 2 km, 4 were built in the steeper section of about 400 meters. The height and diameter of the towers had to meet the requirements necessary to guarantee the pressure necessary to operate the milling system.
The channel expansion works are evident here to allow the addition of other milling systems to those already existing. The green arrow indicates the existing channel and the red arrow the next with a greater flow
in the Valley there were no ruins of houses but only manufactured goods for productive activities, this means that the Valley was an "ante litteram" industrial district where the availability of water as a driving force allowed the activities in which it was necessary to have a lot of energy without interruption. It is not a mistake to think that there were other processes in the Valley, even if we do not have certain data on this aspect.
In the Mulini valley something was realized that has never been replicated in history. A productive set of industrial ecology in which the mills used the energy supplied by the most elementary of natural elements such as water, for their activity. An energy used but not consumed, something that subsequent progress has not been able to replicate.
At the beginning of the 19th century technological progress provided other sources of energy (steam, electricity), so it was no longer necessary to be near the rivers to dispose of energy, and a new tax on milling imposed after the Unit of Italy, which counted the number of turns of the wheel and not the amount of ground flour penalized the small mills in favor of the largest located on the great rivers and that was how the Valley lost its industrial value, which was then due to its progressive abandonment .
The Valle dei Mulini is a part of the path of the ancient path that from Castellammare reached Amalfi, along the Vernotico river. Wayfarers were able to water the pack animals before starting the steep climb to reach their destination. Moreover, the presence of numerous sources on an optimal slope, will allow the construction of a series of mills with vertical axis (horizontal wheel) that were operated by the force of the water.
The set of many mills in sequence is the particularity of the place. Not the single Mill used by the local community, but an industrial system designed to produce flour in enormous quantities, which for over six centuries served the purpose for which they were built.
Encyclopedia Treccani
"industrial district" Production system consisting of a group of companies, mainly small and medium-sized, characterized by a tendency towards horizontal and vertical integration and production specialization, generally concentrated in a given territory and linked by a common historical, social, economic and cultural.
The Valle dei Mulini di Gragnano was one of the first industrial districts in Europe.
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