494 IRVING HARDESTY 



gest its shape in transverse section, as though two small segments 

 had been cut out. When not surrounded by water in the model, 

 its weight caused it to rest limply upon the spiral lamina below, 

 but with the trough filled with water, its thin attached edge was 

 sufficient to support it in a horizontal position. It may be noted 

 that the outspanning zone is trimmed so as to gradually taper 

 and is made much narrower in its basal end (BE). 



With the spiral lamina fixed so as to divide the trough into the 

 two scalae, pieces of platinum wire (PW) were forced through the 

 outspanning zone of the leather tectorial membrane at six inter- 

 vals. These wires were bent at right angles and joined by 

 interlocking loops along the inner side of the trough with copper 

 wires (CW) which passed through corks driven into holes bored 

 in wall of the trough at the corresponding intervals (fig. 6). 

 The platinum and copper wires were joined by looping them 

 together to avoid as much as possible the additional rigidity 

 that would be given the membrane by continuous wires, the 

 loops being thought to act somewhat as hinges during movement 

 of the membrane. That end of each of the platinum wires which 

 passed through the outspanning zone of the membrane was 

 arranged so that it could come in vertical contact with the sur- 

 face of a small copper plate (CP) soldered onto the end of a 

 heavier copper wire which passed through a small glass tube 

 (GT, fig. 6) inserted in holes bored vertically through the spiral 

 lamina and the bottom of the trough below. The passage of 

 the glass tube through the bottom was rendered water-tight by 

 forcing it in surrounded by a piece of rubber tubing, and, for 

 the same purpose, the heavier copper wire passed through plugs 

 of rubber which were forced into the glass tube {R, fig. 6) . Each 

 of the six heavier copper wires (with the copper plates affixed 

 upon their upper ends) was inserted below into a small brass 

 block and held by set screw, and the lower end of each brass 

 block had threaded into it an adjustment screw (AS, figs. 5 and 6) 

 by which the copper plate above could be raised and lowered to 

 adjust the contact between it and the end of the platinum wire. 

 The adjustment screws were held fixed by attachment in a wooden 

 strip (}VS) extending along beneath the model. To the lower 



