(1) First, there is the field notebook. This is where the actual numbers are recorded, together with passing observations relevant to the interpretation of these numbers.
Paper is still proving more durable than electronic data.
(2) The journal is a parallel record to that of the notebook—a daily account of events, thoughts, and observations.
(3) Last of the three strata, then, are the publications. Traditionally, in science, these are articles in academic journals leavened with chapters in books. To be successful, a young scientist need aspire to no more than these two forms of output together with their oral versions at interminable conferences and meetings of learned societies.
There came a time in my scientific development, however, when other forms of publication became important: magazines articles, and writing books.
To understand what a real essay is, we have to reach back into history again, though this time not so far. To Michel de Montaigne, who in 1580 published a book of what he called "essais." He was doing something quite different from what lawyers do, and the difference is embodied in the name. Essayer is the French verb meaning "to try" and an essai is an attempt. An essay is something you write to try to figure something out.
If all you want to do is figure things out, why do you need to write anything, though? Why not just sit and think? Well, there precisely is Montaigne's great discovery. Expressing ideas helps to form them. Indeed, helps is far too weak a word. Most of what ends up in my essays I only thought of when I sat down to write them. That's why I write them.
The Meander (aka Menderes) is a river in Turkey. As you might expect, it winds all over the place. But it doesn't do this out of frivolity. The path it has discovered is the most economical route to the sea.
The river's algorithm is simple. At each step, flow down. For the essayist this translates to: flow interesting. Of all the places to go next, choose the most interesting. One can't have quite as little foresight as a river. I always know generally what I want to write about. But not the specific conclusions I want to reach; from paragraph to paragraph I let the ideas take their course.