Dehydrogenation of isolongifolene over 10% PdC, in the vapour phase, at 450-± 5° gave in ∼23% yield a mixture of naphthalenes, consisting essentially of 1-methylnaphthalene (7·5%). 1-methyl-7-isopropylnaphthalene (eudalene, 67·5%), 1-methyl-6-isopropylnaphthalene (2·8%) and 1,6-dimethyl-7-ethylnaphthalene (7·0%). The formation of these products is in complete accord with the structure I advanced earlier