This is fantastic: Google Book Search has full copies of Popular Science magazine, dating back to 1872, available for you to read online.
The very first issue, May to October 1872, covers such topics as The Study of Sociology (by Herbert Spencer, no less - he coined the term "survival of the fittest"), The Recent Eclipse of the Sun, Science and Immortality, and so on.
Link - Thanks Philipp Lenssen!
I'm trying to find the issue that had the plans for a gas engine powered model airplane called "Miss Sicence" or "Miss Scientific" Around 1941,1942 or 1943.
Thanks
Charlie Calvert
sincerely, Norma E. Mizer