A lovely summer day. But I had an appointment with Apple Support.
The good news was that I discovered that I DID have Time Machine backups on an external drive to my iMac.
Vitor, in Portugal, guided me through reinstalling OS Sierra via internet recovery after erasing the hard drive. Then restarting in recovery mode, I started transfer of data from the external to the internal drive.
The rate of transfer diminished to a crawl. I wasn't hopeful.
While waiting, I picked up the September issue of Outdoor Photography, which I've had for at least two weeks but hadn't read. Gosh, one of my photos won a place in the competition of Sublime Weather. But the editorial staff had managed to mix up the photo with a caption for another that I had submitted. I doubt that anyone noticed.