This is just the first free, public domain eBook I checked out at Project Gutenberg, and also the first picture book you should read to your children. My First Picture Book is credited to Joseph Martin Kronheim. The second book I have looked at here is The Practice and Science of Drawing, by Harold Speed, which contains golden nuggets of knowledge.
This looks like a great project. I wonder if they have larger versions of all the images they have scanned. I hope it isn’t one of those casualties of the early digital age in which great ideas were started too soon, before storage capacity and internet bandwidth caught up with them. What if they scanned thousands of images from books and all they have are 500 pixel wide versions or something? Dag. Well according to their blog, Project Gutenberg was founded in 1971 by Michael Hart, who recently died unexpectedly, and who is also the inventor of the eBook. The blog also mentioned they have scanned their 40,000th book, and I checked the image quality available on that one and it is indeed much nicer, here is just a detail of a cool extinct bird from that eBook: