Well, I found a solution.

While poking around various places on the net, I saw mention of the mknod command, I remembered having to use this in the early days of USB support, so I examined the content of /dev, noted the sequences of numbers on the scsi devices, and did the following:

cd /dev
mknod sda b 8 0
mknod sda1 b 8 1


The drive became reachable immediatlely. For some reason, the nodes for sda, sda1, sdb, and sdb1 all went missing. I will be installing the second drive now that I know what needs doing.

I am putting this here in case anyone else gets bit by this irritating little problem.