Catholics to-day are left in no doubt of the importance which the Church attaches to the kind of music she considers suitable for use in her liturgy. Since the year 1903, when Pius X issued his Motu Proprio, the principles governing legislation in this art have been made accessible to all. But in that encyclical a reference is made to other arts besides music and it is stated, ‘The Church has always recognized and favoured the progress of the arts, admitting to the service of worship everything good and beautiful discovered by genius in the course of ages—always, however, with due regard to the liturgical laws.’ Among these things ‘good and beautiful’ the Church has made use of the Art of Colour at all times, and has, moreover, in various places explained her principles and reasons for so doing. References to these principles are scattered among the canonical books, and occur in the decrees of the Congregation of Sacred Rites. They may be difficult to find when they are wanted, but the general principle of using colour as part of the splendour of the liturgy is too well known and accepted to need emphasis. It has always taken its part in the ceremonial, as one instrument in an orchestra, and the gap in the general harmony would be obvious, if it were omitted. Cardinal Schuster, the present Archbishop ofi Milan, dwells on this accumulated harmony when describing the Introit for Whit-Sunday.