  The two-dimensional Ising model is studied at the boundary of a half-infinite
cylinder. The three regular lattices (square, triangular and hexagonal) and the
three regimes (sub-, super- and critical) are discussed. The probability of
having precisely 2n spinflips at the boundary is computed as a function of the
positions k_i's, i=1,..., 2n, of the spinflips. The limit when the mesh goes to
zero is obtained. For the square lattice, the probability of having 2n
spinflips, independently of their position, is also computed. As a byproduct we
recover a result of De Coninck showing that the limiting distribution of the
number of spinflips is Gaussian. The results are obtained as consequences of
Onsager's solution and are rigorous.
