Xov., I 9 1 9 . ] ]?UBLICAT[ONS }~ECEIVED. 707

U. ~'. Bureau of Standa, rds: Scientific paper No. 341. Airplane Antenna Constants, by J. M. Cork, assistant physicist. 15 pages, illustrations, 8vo. Washington, Government Printing Office, I919.

Representation in Industry, by John D. Rockefeller, Jr. Address before the War Emergency and Reconstruction Conference of the Chamber of Com- merce of the United States, Atlantic City, N. J., December 5, 1918. 31 pages, 12mo. No place of publication.

The Piezo,-electric Effect, a New Principle for Telephone Transmitters and Receivers. A. ~¢I. •ICHOLSON. (Session of the .din. Inst. Elec. Engs., October Io, I 9 1 9 . ) - - W h e n certain crystals are compressed in definite directions a difference of potential is de- veloped between their ends. Conversely, when a difference of potential is applied to the same crystals, they elongate or contract. Similar effects are observed when the crystals are in a condition of torsion. This general effect gives a means of conver t ing me- chanical energy into electrical energy and vice versa.

The crystals showing the above effect are hemihedral or hemi- morphic. Those of Rochelle salt are especially good and large specimens can be grown. Under torsion such crystals give a difference of potential of as much as 6oo volts. Desiccated crystals are several times as effective as freshly prepared ones.

The method of t ransmit t ing sound is as follows: A crystal under torsion that the motion of the stylus of a phonograph varies the strain already existing and hence develops a difference of potential between the two ends. Two wires are led from the crystal to a 3-stage amplifier to the other end of which is elec- trically connected a second crystal, likewise under torsion. The varying potential supplied from the amplifier causes the crystal to dilate and to contract. These motions which closely follow the intricate motion of the stylus cause air-waves. Ins tead of the stylus the hurnan voice may be used directly to vary the force act ing on the t ransmi t t ing crystal.

A demonstra t ion of this very significant me thod of sound transmission was given in the Bellevue-Stratford Hotel, Philadel- phia, October Io, I9I 9. The voice of a man by " direct action " as well as instrumental music and the voice of Galli Curci from phonograph records were well rendered. The effect was espe- cially good when the receiving crystal was placed on a bare wooden table. I t was not even necessary to press the crystal upon the support ing surface. The quality of the sounds pro- duced was good.

This was the first public exhibition of the new means of trans- mis.sion and was made only about three days after success had been attained in the laboratory.

G. F. S.