books.google.com is a good one.
Whatever you search, just click on “Search Tools” towards the top, then where it says “Any Books”, drop that down and select “Free Google eBooks
Here’s a search for “Clock Making”, yields lots of 1800s books.
http://www.google.com/search?num=100&hl=en&tbs=bkv:r&tbm=bks&spell=1&q=clock+making&sa=X&ei=pjskUdrhIqvs2AWa44G4DA&ved=0CDUQBSgA&biw=1280&bih=574
If you search “Clockmaker”, “Watchmaking” you will get different stuff. If you want to search it all at once, just type in OR in between (in capitals) the words (clockmaker OR watchmaker OR watchmaking OR clock making