A scientist working on an invention is engaged in the activity of-blank-out.

Instead, he is working on a dangerous invention.

"It's the first time I remember when he worked on an invention without telling me something about it," mused Ned.

I believe he's working on a new invention that requires some specialized machinery.

"When I'm working on an invention with you, pal, I hardly know whether it's today, tomorrow, or yesterday!"

Also, if Murray worked with anyone else on an invention, their name would be listed on the patent.

The commander was working on a tremendous invention: a submarine that would travel by almost automatic propulsion.

He's working on a rather important invention.

He was working on a new invention, a disintegrating ray with which he had gained some success.

I can't have strangers prowling about here, now that I am going to get to work on a new invention.