We had a husky Honda generator out in a concrete-block shed. It sat unused much of the year, till we needed it , during deer season, to power the lights, refrigerator, and water pump. One late fall day it wouldn’t start. I groaned inwardly, anticipating several hours of dismantling and guessing.

“No problem,” Charlie explained. “It’s gotta be one of three things: air, fuel, or spark. So we start with the most likely and the easiest – air.” He took off the air cleaner and looked inside. It was packed full of leaves, moss, and grass. The woodshed mice, not much into mechanical matters, had chosen it for their winter home. Charlie evicted them, put the air cleaner back on, and we were again in business.

That was probably thirty years ago, but that simple, logical approach to problems has stayed with me. It’s exactly the same as Conan Doyle’s: Sherlock Holmes, faced with a criminal conundrum, first eliminates all the impossible answers, and what’s left is invariably the right one. To the uninitiated, both Sherlock and Charlie might seem to be wizards or necromancers. Far from it. Like Carl Sagan, for example, who could explain the cosmos to us earthlings in our own language, they’re just geniuses.

I thought of Charlie this week as I trudged, cane-assisted, up the gravel road to the summit of Hubbard Park, a local favorite and the almost daily resort of me and Kiki, who covers roughly fifty times as much country as I during our walks. Ten years ago I often tramped briskly up and over the summit, past its tower, and down the other side to the State House. Then back over the same route back to the car; elapsed time about fifty minutes. Nowadays I think I’d have to pack a lunch, and I’d certainly carry my LifeAlert.

Like many of my friends now over life’s summit ridge and shambling down the back side, I’m familiar, probably, with all the slogans and maxims that once seemed unlikely to be relevant to my condition, but now are no longer funny. Way back in the early Fifties our cross-country coach said, “The legs are the first to go.” Fit as fiddles at the time, we doubted that. Then there was the hilarious line, “Help! I’ve fallen and I can’t get up!” When I scrubbed my floor-level freezer a couple of months ago, the humor drained completely out of that scenario. Not to mention when I toppled over sideways recently from my cross-country skis into deep, soft snow. That was even scary; there was nobody anywhere around.

Now I frequently come across, “Old age is not for sissies.” It seems to me the height of ingratitude after a long life to grouse about its challenges. I may miss my late wife to the point of tears at times, but I’m pretty happy still to be here, even alone. The aches and pains and leaks and weakness clamp with an ever-tighter grip, like that of one of those plaited Chinese finger-grabbers we used to play with as kids. But there remains so much! Tennyson’s Ulysses says it best, as he calls to his aged shipmates to set sail once again, “beyond the sunset, and the baths of all the western stars.” What sort of churl would resist that summons?

So, while Kiki scours the woods around me, removing all existential threats, I marvel at the beauty of her bounding flight and plod on, thinking, strangely of Charlie. What are the problems of age, if not obvious? Why do I feel I’m struggling some days, while hopeful on others?

I can imagine Charlie asking, “How’s your air intake?” Well, that’s fine. The occasional winter wheezing, a result of years of inhaling sheetrock and concrete dusk, is in remission for now.

Fuel? Hardly a problem. If there is one, it’s that, like most of us, I run best on regular, but prefer high-test. So I’ve been operating on a leaner mixture lately. It’s not that.

Which leaves spark, which is a tricky problem. There’s no way to know how many hours I once spent under my Plymouth’s hood, fiddling with plugs, coil, condenser, and distributor. At least she didn’t die of any of those. The spark that in old folks makes us go, and keeps us going, is far more complicated. We know – or at least we’ve been told – that group activities are the answer: yoga, choral singing, exercise, travel, Scrabble tournaments. But the pain of losses, the creature comforts of a good book or crossword puzzle in a chair by a window, and the fear of the results of an adventure – I think of John Steinbeck and his Charley – all militate against that spark we so desperately need to keep the engines going.