set-global-staff-size equivalent for a single \score (e.g., within a \book)?

[Kieren MacMillan]

Hello, all --

Is there any way to declare the staff-size on a per-score basis,  
instead of globally using #(set-global-staff-size X)?
e.g., something like

\version "2.9.10"
\score
{
        { a4 b c d }
        \layout
        {
                #(set-staff-size 18)
        }
}

\score
{
        { a4 b c d }
        \layout
        {
                #(set-staff-size 10)
        }
}