There is disclosed a vessel having a plurality of cryogenic tanks for the storage of liquefied gases wherein the cryogenic tanks are provided with conduit means and a heat exchange means whereby the unavoidable boil-off from a lower boiling liquefied gas stored in a first cryogenic tank means, is passed in indirect heat transfer relationship with the unavoidable boil-off from a higher boiling liquefied gas stored in a second cryogenic tank means, to re-liquefy the vapors of the higher boiling liquefied gas. Additional conduit means are provided to permit alteration of the gaseous atmosphere in the second cryogenic tank means (after un-loading its content) to the atmosphere of the liquefied gas to be subsequently stored and transported therein.