  We study the energy current in a model of heat conduction, first considered
in detail by Casher and Lebowitz. The model consists of a one-dimensional
disordered harmonic chain of n i.i.d. random masses, connected to their nearest
neighbors via identical springs, and coupled at the boundaries to Langevin heat
baths, with respective temperatures T_1 and T_n. Let EJ_n be the steady-state
energy current across the chain, averaged over the masses. We prove that EJ_n
\sim (T_1 - T_n)n^{-3/2} in the limit n \to \infty, as has been conjectured by
various authors over the time. The proof relies on a new explicit
representation for the elements of the product of associated transfer matrices.
