On the Motion and Measurement of Water

LEONARDO DA VINCI 278

CHAPTER IX.

The center of the sphere of water is the true center of the roundness of our World, which is composed of both water and land in a round shape. However, if you wished to find the center of the element of land, this is determined by a distance equidistant from the surface of the Ocean sea, and not from the equidistant surface of the land; for it is clearly understood that this globe of the earth has no point of perfect roundness except in those parts where there is the Sea, or marshes, or other still waters; and any part of the land that rises out of that sea moves away from its center.

CHAPTER X.

We see the Nile starting from the southern regions and marking various provinces, flowing toward the North for a distance of 3000 miles, and emptying into the Mediterranean Sea of Egypt. And if we wish to give this a drop of ten cubits brazza: an old Italian unit of measurement, or "cubit," which Leonardo used to calculate the gradient or slope of rivers per mile—which is the amount commonly granted to the general flow of rivers—we will find that the end of the Nile is ten miles lower than its beginning. Furthermore, we see the Rhine, Rhone, and Danube starting from the German regions, almost at the center of Europe; one flows to the East, another to the North, and the last to the southern seas. If you consider everything well, you will see that the plains of Europe form a gathering point that is much more elevated than the high peaks of the coastal mountains. Now think how much higher their peaks must be than the sea shores. Therefore, etc. Leonardo is arguing that the land must be significantly "higher" than the sea level for rivers to flow such distances, meaning the center of the solid earth's mass is not the same as the center of the water's sphere.

CHAPTER XI.

It can be both straight and curved, provided that in its motion it moves closer to the center of the World; for if it did not do so, that water would remain motionless, unless it were a reflux original: "corso reflesso"; referring to a backward flow or tide, and I do not take this into account because it is a forced motion moto violento: in Renaissance physics, a "violent" or forced motion is one caused by an external power, as opposed to "natural" motion caused by gravity. It is proven that if OCR These letters refer to a geometric diagram in the original manuscript is a mountain, from the...