He attended lectures on the numerical solution of equations and on definite integrals by M.
He appears to have attended Dirichlet's lectures on theory of numbers, theory of definite integrals, and partial differential equations, and Jacobi's on analytical mechanics and higher algebra.
He also showed that every equation of an even degree must have at least one real quadratic factor, reduced the solution of linear differential equations to definite integrals, and furnished an elegant method by which the linear partial differential equation of the second order might be solved.
The integrals are then properly functions of the direction in which the light is to be estimated.
If when the aperture is given, the wave-length (proportional to k1) varies, the composition of the integrals is unaltered, provided E and n are taken universely proportional to X.