  Beauville and Laszlo give an interpretation of the affine Grassmannian for
Gl_n over a field k as a moduli space of, loosely speaking, vector bundles over
a projective curve together with a trivialization over the complement of a
fixed closed point. In order to establish this correspondence, they have to
show that descent for vector bundles holds in a situation which is not a
classical fpqc-descent situation. They prove this as a consequence of an
abstract descent lemma. It turns out, however, that one can avoid this descent
lemma by using a simple approximation-argument, which leads to a more direct
prove of the above mentioned correspondence.
