Some of the images are now broken links. I've come to the conclusion that without some clear statement of permission to use or of public domain status, I've no clear right to show those images. Historical originals are uncopyrighted, of course, but reproduced images may be copyrighted and even if not, someone might feel agrieved that they circulate on the web. The images linked by thumbnails are legitimate to use for personal educational purposes with credit or are public domain. The thumbnail link gives the credit and link to the source if needed.