Leonardo Da Vinci by Kathleen Krull Page A

that what he could see with the naked eye requires high-speed photography to record.
    Watching waves—and depicting them in beautiful, curling drawings—led him into areas such as meteorology and geology. He seemed to have understood the principle of erosion, describing the way waves carry sand away and the way water “gnaws at mountains.” He learned the effect of the moon on the tides, speculated about continent formation, and analyzed the nature of fossil shells found on moun taintops. One would think that, with his artistic eye, he would have been most interested in the beauty of shells and fossils—their forms and patterns. But he was after something else: to understand why they were there at all.
    Leonardo grasped the principle that flooding water deposits layer upon layer of sediments (soil and sand), which turn into rock. At the same time, rivers erode rocks and carry their sediments to the sea, in a continuous cycle. He wrote, “The stratified stones of the mountains are all layers of clay, deposited one above the other by the various floods of the rivers.”
    In Leonardo’s day, there were two theories about why fossils and shells were found in rocks on the tops of mountains. Some people believed the shells were carried there by the biblical Flood; others thought that these shells had grown in the rocks.
    Leonardo pooh-poohed both hypotheses—such opinions “cannot exist in a brain of much reason.” From his direct observation of shells and fossilized seaweed during walks in the Italian Alps, he came up with a third theory, one that is closer to the modern one. Shell fossils were once living organisms that had been buried at a time before the mountains were formed: “Where there is now raised land, there was once ocean.” To Leonardo, as to modern paleon tologists, fossils indicated that the history of the earth extended far beyond human records (such as the Bible)—“things are much more ancient than letters.” Such theories would have offended a strict religious sensibility, as would his scrutiny of Bible passages for lack of scientific logic.
    One day Leonardo wrote, “The sun does not move,” in large letters on a page all by itself. We don’t know exactly what he meant by this. He wasn’t sure—he contradicted himself elsewhere in the notebooks. But was he beginning to question Ptolemy’s ancient and still-popular view that the sun moved around the earth?
    The notebooks covered a wealth of miscellaneous offerings—whatever interested Leonardo’s butterfly mind. He tried to come up with a formula for making a synthetic material, something like plastic. It combined saffron, poppy dust, and whole lilies boiled together with eggs and glue.
    Numerous themes, however, recur over and over: for example, the manipulation of nature through technology. The pages detailed all sorts of machines he designed with gears, cogwheels, screws, and pulleys. He invented a bicycle that would have really worked. He borrowed freely from what others were doing at the time (as he did in all fields), but never without questioning the work or trying to improve it. Machines of all sorts fascinated him. In fact, Leonardo viewed the human body as a machine—the ultimate machine—capable of being understood by looking at its different parts.
    Leonardo wanted to find new sources of energy. In an era when the main source of power was muscle (of men and horses), he looked at new ways of using water, wind, and steam. He constructed a device to measure the volume of steam coming off a certain quantity of boiling water. Some think he anticipated the invention of the steam engine hundreds of years later; at the very least, he understood the concept of steam as power. He also proposed using solar energy, trapped by mirrors he invented, to help out the textile industry.
    And, of course, there was mastery of the air, his favorite and most obsessive dream. His notebooks played endlessly with this theme. He drew parachutes, gliders