Different voltage I2c lines

So a topic that i havnt seen discussed,

Im trying to connect a 3.3v bmp180 and a 5v clock module to i2c lines. I put 4.7k resistors between the 5v power and i2c lines.

Nothing works, how do i handle 3.3v and 5v sensors to the same I2c lines.

Thanks!
Kennedy

http://playground.arduino.cc/Main/I2CBi-directionalLevelShifter