In the case of composite colour, an infinity of systems must be obtained for maxima infinitely slight and with an infinity of interval values separating them - that is to say, the whole thickness of the sensitive layer is occupied in continuous manner by these maxima.
Gabriel Lippmann[On the Gaussian curve, remarked to Poincarรฉ:] Experimentalists think that it is a mathematical theorem while the mathematicians believe it to be an experimental fact.
Gabriel LippmannThe problem of direct colour photography has been facing us since the turn of the last century.
Gabriel Lippmann