As I write these lines, I have begun the process of grading my students’ final efforts in the classes I am teaching. The process will continue until May 9 when grades for graduating seniors are due. It will take up most of my work time until then.

I had expected the work to be tedious and painful, but I find myself hanging on every word of their writing journals, revisions, portfolios and final projects.

The mound is huge. It will get even higher over the next few days, but I don’t mind. This semester, I have the joy of teaching a course in writing about science for a popular audience, a course I have longed to teach for 20 years.

I will be retiring from my job at Perkins Observatory July 31. I won’t be teaching during the fall semester. Afterward, I will be teaching on a limited basis and only during spring semesters. Today, I begin to grade the last essays I will read as a full-time employee of Ohio Wesleyan University, a place I have grown to love.

As I grade the essays, an old black-and-white video flits through my head. As he retires, General Douglas MacArthur speaks before Congress. “Old soldiers never die,” he says. “They just fade away.” Old teachers never die. They just go into semi-retirement.

Still, grading the essays feels like I’m standing at a terminus. I make a mental note to look up the word terminus to make sure I’ve used it correctly in this context. Joe Musser, an honored, retired professor from the English Department at OWU, reads my column every week. (Hello Joe!) It will not do to embarrass myself in front of one of my beloved mentors.

I must get back to grading. Tonight looks to be a clear one, and the stars will shine brightly. I need a break, but I do not want to stray far from my task. So, I will do a bit of stargazing from my backyard.

I will first find the royal constellation Leo, the Lion. Easy enough. He shines brightly high in the southern sky just after night has fallen. I will save for later his brightest star, Regulus, which forms the front paw of the Lion.

Instead, I will examine the lion’s tail, the star Denebola, 40 light years away. Forty years ago, its light erupted from the surface of that star and began its long journey toward my eyes. About that long ago, I graded my first essay, an inarticulate effort about courage by an 18-year-old, first-year student.

And thus the years have passed — two-thirds of a lifetime to me, but a finger snap to a star like Denebola, which has graced our earthly sky for billions of years and will still shine there long after I — and, most likely, we — are gone.

No time to think about that now. Must get back to grading. But as I mark the papers, my mind wanders back 40 years to that first essay.

As a novice teacher, I sit in my decrepit office at Ohio State and grind through a poorly written effort so full of error that I have to read it several times. Each time I read it, I peel away another layer of grammatical weirdness until at last I get to some hint of meaning.

As a result, I remember that first paper well. It begins, as many first-year college essays have begun before and since, “The dictionary defines courage as … .”

“Don’t tell me what the dictionary says,” I write. “Tell me what you (underlined twice) say. Describe some examples of courage. Give me details. Show me. Don’t just tell me.”

I look up, my eyes glazed, as I think now of that essay on courage and the utterly confused student who wrote it and the utterly confused teacher who read it.

I look down again and see the following words, written by a current student about black holes: “That blackness becomes a mirror to see everything you know against the darkness that could have been.”

And in that momentary glance upward and then downward again, 40 years have passed.

I look up the word terminus in a dictionary and shamelessly do now what I have begged my first-year composition students never to do in their writing.

The dictionary defines terminus as “1. The end of a railroad or other transportation route, or a station at such a point; a terminal” and “2. A final point in space or time; an end or extremity.”

Even though I will teach again in eight months, this moment feels like a terminus. The journey has been so long and so short, sometimes painful, often joyful. As I leave, I linger at the gate, look back, and remember.

I bear down again on my students’ essays. Doing so requires an odd and hopelessly indefinable kind of courage. Finding it, I begin to devour every word as if it is the last one I will ever read. Circumstances require that I must not linger. I linger anyway.