Decoding Newton’s writings: applying a different calculus and science to dating his manuscripts. From the article:

What were described at [Newton’s] death as “reams of loose and foul papers” have over the years been organized by their custodians. For instance, some of the first collectors, including economist John Maynard Keynes, tried to regather the manuscripts by focusing on theme (alchemical manuscripts in Keynes’s case). More recently, large-scale digital humanities projects have been reuniting the manuscripts—if only in virtual form—and organizing them by subject and other criteria.

The oldest and largest of these digital ventures is the Newton Project, now based at Oxford University. Created in 1998, the project has transcribed more than four million words of Newton’s writings, primarily those in physics, mathematics, and theology. Working in tandem with the Newton Project is the Chymistry of Isaac Newton at Indiana University, an undertaking to produce a similarly comprehensive, web-based edition of Newton’s papers but limited in scope to alchemical manuscripts….

Watermarks aren’t the end of the tools at our disposal to make order out of Newton’s manuscripts. For many years scholars have tried to date Newton manuscripts based on changes in his handwriting over his lifetime, but this method is now considered unreliable. However, there is still some value in this approach….

Newton made his ink from oak galls, gum arabic, copperas (impure iron sulfate), and beer. Needless to say, none of these were laboratory-grade reagents, and we would expect the chemical composition of the ink to vary considerably from batch to batch. So, is there a nondestructive way to distinguish different batches of Newton’s ink? This kind of information would be helpful in situations where Newton may have revised his notes months or years after their initial composition.

The answer is, we hope, yes, and the method of choice is X-ray fluorescence spectroscopy (XRF). In XRF a sample is bombarded by X-rays. When an X-ray dislodges an electron in one of the lower energy states in an atom, an electron in a higher energy state will repopulate the lower level, but to do so the electron must discard some energy in the form of a photon. The X-rays emitted when changing from one energy level to another are characteristic for each element. By collecting a range of X-ray energies coming back from the sample, the XRF spectrometer can determine both the elements in a sample and their proportions. By plotting characteristic ratios of iron, copper, and zinc in Newton’s ink, we hope to be able to identify and date different batches and so reveal the relationship between manuscripts and, consequently, when they were written….

It is charming to think now that those tiny atoms, either the chemical impurities in the ink with which he wrote those words or in the semiconductors in the imaging and computer systems used to analyze them, are providing the means to make sense of the writings of the man who conceived them.

h/t Anna Honer