Virtual Villagers Tips & Tricks, Walkthroughs, Guides, Hints and HelpLast Day of Work Official Forums: Virtual Families, Virtual Villagers, Fish Tycoon
The observatory puzzle is definitely a challenging one!
To make the cog,
Click to reveal..
drag and drop an adult villager on the wooden log. You'll need to have already moved the log to the observatory base and crafted the saw, while your village's crafting and research technologies should both be level 4.