This aerial photo by our friend Gianni Cesariello is very interesting because it allows to notice an important detail that was not present on the other mills. I am referring to the presence of two vertical ducts instead of just one as for other mills and, at the same time, the closure of the main well (almost certainly filled with inherent material) can be clearly seen, transforming the upper part into a collector pit which distributes the water to the two funnels.
The cleaning work of other mills will certainly lead to the discovery of other interesting details, which will enrich the knowledge of hydraulic technique which had its greatest development in the Valley.
We already knew that the Mills were subjected to a great deal of expansion work starting from the canals which were modified to allow for a greater flow of water and therefore, as with all the others, a second millstone was added in this Mill too but perhaps due to structural problems or For another reason (which escapes to me at the moment), here it was decided to eliminate the main well and create two vertical ducts.
In this phase of expansion of the mills an important aspect was the use of large funnels at the top of the vertical pipe. The collector created on the previous well had the task of ensuring that the water did not enter by gravity but was "evened" at the top to eliminate air bubbles in the descent pipe. This would have reduced the impact force against the water wheel.
The vertical pipes were bottomless terracotta vases inserted into each other and then covered in tuff. That is because the continuous passage of water would have consumed the (black) tuff which, moreover, is of poor quality compared to the yellow one of the Phlegraean area .
The use of the tuff for these extensions allows us to date, albeit approximately, after the original constructionin limestone.