We only know what you wrote. We can only guess what you might have meant.
"Donald G. Shead" wrote:
> Uncle Al <UncleAl0@hate.spam.net> wrote in message news:<40B9214C.83836F50@hate.spam.net>... > > "Donald G. Shead" wrote: > > [snip] > > > > > The singular possessive of mass is either mass' or mass's. > > The plural possessive of mass is masses'. > > Did anybody NOT know that's what I mean(;^?