How do I overlay 2 different translucent clips?

[super werty]

Sorry if this has been covered before, I tried a search but was unsuccessful at finding an answer.

I'm using FCE4

What I have is two different videos of a truck speedometer accelerating. I basically want to show a before and after simultaneously. I dont want two clips side by side. I need to find a way to make one of them or maybe both clips translucent, so you could see how much faster the needle was accelerating. I thought this was called superimposing, but when I did a search for that I found a lot of confusing answers.

Am I making any sense?

Any help would be appreciated

 

[J the Ninja]

Lay them on top of each other as two separate video tracks. Then double click the top on to open it in the Viewer, and go to the "motion" tab. There should be a slider there labeled "opacity". Does that do what you want? If not, do you have an example you could link to?