Help with rays?[Not fixed]

So I saw this tutorial on the wiki that showed about raycasting,so then I tried to do my own raycasting and I got a error saying:

18:21:54.179 - Workspace.Script:1: bad argument #2 to 'new' (Vector3 expected, got number)

Script:

local Ray = Ray.new(game.Workspace.Part.CFrame.lookVector.unit,--the ray will start at this part
game.Workspace.Part.CFrame.lookVector.unit)--Ray will come out of the front

local hit,position = Workspace:FindPartOnRay(Ray,_)

print(hit.Name)--print name of thing that the ray hit

Why did I get this error and how do I fix it?