Top panel: principal modes of energy transportation through a C-type shock wave of speed v_s = 25 km s^-1, propagating into molecular gas of density n_H = n(H) + 2n(H₂) + n(H⁺) = 10⁵ cm^-3, with an initial transverse magnetic field strength B = 316μG. Second panel: thermal and density profiles. Third panel: rates of cooling by the main coolants, per unit volume of gas. Bottom panel: fractional abundances of these coolants, relative to n_H.