SOME ASPECTS OF VARIATIONAL SEQUENCES IN MECHANICS Raffaele Vitolo Key words: Fibred manifold, jet space, variational sequence, Euler--Lagrange map, Helmholtz map. 1991 Math. Subject Classification: 58A12, 58A20, 58E30, 58G05. Abstract: We discuss intrinsic aspects of Krupka's approach to finite--order variational sequences. We recover in an intrinsic way the second--order variational calculus for affine Lagrangians by means of a natural generalisation of first--order theories. Moreover, we find an intrinsic expression for the Helmholtz morphism using a technique introduced by Kol\' a\v{r} that we have adapted to our context.