As all these tone producers are enclosed in a thick Swell box, an artist is able to employ them with as much refinement of effect as is heard when they are heard in a Symphony Orchestra. Mr. Hope-Jones informs the writer that he has just invented an electric action which strikes a blow accurately proportioned to the force employed in depressing the key, thus obtaining expression from the fingers as in the pianoforte. He will apply this to the percussion stops in organs he may build in the future. When skilfully employed many of these percussion stops blend so perfectly with the flue and reed pipes that they become an important integral part of the instrument--not merely a collection of fancy stops for occasional use. THE DIAPHONE. The invention of the Diaphone by Hope-Jones in 1894 will some day be regarded as the most important step in advance hitherto achieved in the art of organ building. The existence of patents at present prevents general adoption of the invention and limits it to the instruments made by one particular builder. In addition to this the Diaphone takes so many forms and covers so large a field that time must necessarily pass before its full possibilities are realized. Enough was, however, done by Hope-Jones in connection with the organs he built in England a dozen or eighteen years ago to leave the experimental stage and prove the invention to be of the greatest practical importance to the future of organ building. The author's opinion that before long every new large organ will be built upon the Diaphone as a foundation, is shared by all who have had opportunity to judge. By no other means known to-day can anything approaching such grand and dignified Diapason tone be produced. Were twenty large Diapasons added to the instrument in Ocean Grove, N. J., or to that in the Baptist Temple, Philadelphia, and were the Diaphone removed, the instrument would suffer most seriously. In the Pedal department no reed or flue pipe can begin to compare with a Diaphone, either in attack or in volume of tone. In Figure 23 we give a sectional view of the first large Diaphone made, namely that constructed for the Hope-Jones organ in Worcester Cathedral, Eng., 1896. [Illustration: Fig. 23. Diaphone in Worcester Cathedral, Eng.] M is a pneumatic motor or bellows to which is attached a rod bearing the compound and spring valve V, V|1|, working against the spring S. On the admission of wind (under pressure) to the box A, the motor M is caused to collapse, and thereby to open the valves V, V|1|. Wind then rushes into the chamber B, and entering the interior of motor M through the passage C, equalizes the pressure in the motor. The action of the springs now serves to close the valves V, V|1|, and to open out the motor M, whereupon the process is repeated. [Illustration: Fig. 24. Diaphone in Aberdeen University.]