  We provide, for any $r\in (0,1)$, lower and upper bounds on the maximal
density of a packing in the Euclidean plane of discs of radius $1$ and $r$. The
lower bounds are mostly folk, but the upper bounds improve the best previously
known ones for any $r\in[0.11,0.74]$. For many values of $r$, this gives a
fairly good idea of the exact maximum density. In particular, we get new
intervals for $r$ which does not allow any packing more dense that the
hexagonal packing of equal discs.
