By The Metric Maven

In my single digit youth I often walked across the “old bridge” in my small town. One could see right off of the concrete bed of this truss type bridge over the Iowa River. I noticed that a small dam existed with an opening near the center of the river. People would often walk out on this dam, which had a height of only 1 to 1.5 meters or so, and fish. One day in the local library I saw a painting that showed an old mill had been on the river. I was quite surprised and asked if it had really been there. The librarian said it had, and was washed away during a flood.

It was a decade or so later that I learned photographs of the “old mill” existed. One of them is inset above. On the far right side of this photo is the location of the “new mill.” A local history1 offers little detail about the design of the “old mill.” Before the old mill, there was an original mill. A dam was constructed and:

The river provided the power for the first flour and sawmill built in 1855 or early 1856 by Dr. Cutler and Archer Dumond.” … “After only a few months’ use, this first mill constructed by the early settlers was washed away by flood waters in the spring of 1856.

In 1857, the next mill constructed was a steam mill. The following year, 1858, was so wet that the steam mill was surrounded by water that season. The machinery was sold and moved to Kansas. Apparently, rather than use the river for a source of power, an experimentation with steam took place.

The “old mill” in the photograph was constructed on the site of the “original mill” in 1858 by G.H. Armsbury. It was both a sawmill and gristmill. It is not stated if it was a water powered mill, but judging from the details of the transaction, it probably was. In 1863, George A. Thompson took charge of the gristmill. His relative Joseph Fulton became a part-owner of the mill, which, in 1870, was the only flour mill in Wright County. In the Spring of 1870 Fulton became entangled in the mill workings when he went to the basement to oil some of the parts. He was killed instantly. Assuming this is a mill that utilized a flat mill stone, they could revolve up to 125 RPM, with a considerable mass.

The mill dam was renovated numerous times before the “old mill” was finally retired. The “new mill” was constructed about 1901 and the “old mill” was:

….being torn down. The timbers are rotting away and it would soon be at the mercy of the first serious wind storm. In the days of long ago, it furnished flour to farmers as far away as Spirit Lake.

The last mill in Belmond Iowa was torn down in 1935, the location of the final millstone is a mystery. The bridge I traversed as a boy was the only structure left from this time period. It was replaced decades ago. I suspect the millstone was a flat affair that was common at this time. It is my understanding that some people actually collect old mill stones which have many unique cutting patterns rendered on their surface. Grain would be fed into the hole at the top. It would work its way down into the meeting line of the rotating upper stone and the static lower one. The milled grain then worked its way outward where it was collected.

I thought about this local history when I was re-reading The Ancient Engineers by L. Sprauge de Camp. The grinding of grain was of paramount importance to the creation of bread. This was a consistent staple: (page 243)

“…Throughout the ancient empires, bread was the principal food. To make it, wheat or barley grain had to be ground into flour. At first the grain was painfully pounded with a pestle in a mortar, as you can still see done in Central Africa.

At a later time, the grain was ground between two flat stones, one of which was pushed back and forth over the other. With such a mill, one person—usually a slave girl—could grind each day only enough grain to make bread for eight people. Hence, in a large household, several such women would have to spend their entire day at the weary task of pushing and pulling the upper millstone. The two ever-present sounds of ancient households were the clack of the loom and the grate of the hand mill.”

The implementation of water power to grind grain, is a perfect example of employing engineering to help keep a community fed, and reduce the horrible mind-numbing boredom of an essential all-day repetitive task.

All of the examples of millstones I had seen were a pair of stone cylinders with a flat interface between them. The small hand versions are called quern-stones. The large millstone examples I had seen using water power were always like this. One stone had patterns cut into it for the grain to be ground and then work its way out from the center where it could be collected by a pan at its edge.

I encountered a pair of surprises when L. Sprauge deCamp offered this drawing of a hand mill from ancient Pompeii:

This is known as an hourglass mill and was used in Hellenistic and Roman times. I was quite surprised that it was possible to make stone conform to these shapes, but what really confused me were the dimensions. Throughout The Ancient Engineers, all the dimensions are in Ye Olde English. The book was published in 1960, so this is not surprising, but what on Earth were the units m/m? I knew that ca. meant “approximately,” or “about this dimension,” but m/m was strange. I hypothesized that it was millimeters—even though the entire complement of the book is in Olde English measures. The values 900 mm and 700 mm seemed to make approximate sense. What is wonderful about our modern world is that I can do a web search on hourglass mills and see photographs of the mills at Pompeii:

The dimensions in millimeters found on the drawing make sense, but the use of m/m for millimeters was unknown to me at that point. I consulted with Peter Goodyear, and he found examples of guns drills, and clocks that are still designated with m/m for millimeters! I have no idea where the designation m/m originated, but amazingly it is still in use. Indeed here is a specification table from a Tawianese company that makes paper cutters:

I’m pleased they used millimeters, but amazed and annoyed that m/m is used for mm. This is another example of an introduced usage from another era that continues to complicate our modern world in an unnecessary manner. It also demonstrates just how hard reform that would simplify our world is to achieve.

[1] History of Belmond, Iowa 1856-2006 Belmond Historical Society

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The Metric Maven has published a new book titled The Dimensions of The Cosmos. It examines the basic quantities of the world from yocto to Yotta with a mixture of scientific anecdotes and may be purchased here.