How to pass Array{Array{Float64,1},1} to ccall double**

For double*, I find it is easy to use Ref{Cdouble}. But for double**, when I use Ref{{Ref{Cdouble}}} and pass Array{Array{Float64,1},1} . It gives an error

MethodError: Cannot convert an object of type Array{Array{Float64,1},1} to an object of type Float64

What is the right way to pass this pointer? Thanks