That's right. 137 years of Popular Science magazine available to download for free.
From the Popular Science web site:
"We've partnered with Google to offer our entire 137-year archive for free browsing. Each issue appears just as it did at its original time of publication, complete with period advertisements. It's an amazing resource that beautifully encapsulates our ongoing fascination with the future, and science and technology's incredible potential to improve our lives. We hope you enjoy it as much as we do."
EDIT: An updated link to Google Books listing for this has been found here: