880 



SCIENCE 



[N. S. Vol. XXVI. No. 677 



3 mm. thick. Next there is (3) a dead air 

 space from 2 to 3 cm. thick. Layer 4 is a 

 ■wood partition, 2.5 cm. thick. The outer- 

 most layer (6) is a special composition of 

 ground cork, Korkstein, 6 cm. thick. The 

 euter surface of the last layer is plastered, 

 probably mainly for appearance. The space 

 between layers 4 and 6 is filled with a mixture 

 of ground cork and sand. The thickness of 

 this mixture is 4 cm. The total thickness of 

 the walls is, therefore, about 11 inches. 



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 '////,%'/////.'. 



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wym, 





a Tricjjoplese. 



Cork iSa 



■ V.vy'-/-/-'/'^r:/\ Poroi^i Stone. IJSJjvj^iijiJf^l Korkstein 

 W//m///M Wood. 

 Leaa. 



iz 



Fig. 2 



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i5pace 



The ceiling is more simply made, but it has 

 an analogous " double-wall " construction. 

 From within outwards there is (1) Trichopiese, 

 (2) wood ceiling, to which the Trichopiese is 

 fastened and which in turn rests on the porous 

 stone of the inside layer of the walls, (3) 

 sheet lead, 3 mm. thick, (4) an air space, (5) 

 a second wood ceiling, which is covered with 

 (6) asphalt paper, (V) sea grass and (8) 

 Korhstein. ' 



The floor is the least satisfactory part of the 

 construction. The floor of the old room had 

 to he used. To prevent vibrations passing 

 from board to board the joints were sawed 

 through and the crevices thus made were filled 

 with lead. The whole floor was then covered 

 with a layer of lead, 3 mm. thick, and over 

 this a very thick (1 cm.) carpet has been 



placed. At times a second carpet is also used. 

 Had the original floor been of marble or 

 cement it is probable that the two layers (lead 

 and' carpet) would have been as satisfactory 

 as the six layers of the walls. 



The door is double. The outer part opens 

 on the corridor. It is an ordinary door, made 

 of wood, but accurately fitted with felt. The 

 inner door is composed of three layers. The 

 middle layer is wood, the inner or room layer 

 is Trichopiese^ and the outer layer is Korh- 

 stein. This inner door opens into the room. 

 There is the usual air space between the two 

 doors. The door is part of one of the long 

 sides of the room. 



Nearly opposite the door is a small rect- 

 angular window, 38 by 45 cm. This opens into 

 the small adjoining room to the south and is 

 directly opposite the window in the roof. 

 The roof window opens to admit light and air, 

 but the opening is covered with a fine gauze 

 screen to exclude insects and especially moths. 

 When both windows are open the sun can get 

 into all comers of the room and the room may 

 be partially ventilated. With doors and 

 windows open the room is thoroughly venti- 

 lated. 



The sound stimuli may have their origin in 

 or outside the sound room. If the source of 

 the sound is in an adjoining room the appa- 

 ratus is placed in a cabinet, isolated from the 

 floor by a lead plate and felt, and covered with 

 the same materials. This isolation still 

 further decreases the chance of these noises or 

 tones entering the room through floor, ceiling 

 or walls except in the manner that is desired. 



For experiments in which it is necessary to 

 have the origin of the sound stimuli at a dis- 

 tance from the subject means are needed for 

 conducting the sound into the room. For this 

 reason a hole was bored through one of the 

 walls and a copper tube inserted. This tube 

 is fastened to a marble plate, which in turn is 

 fastened to the second layer, porous stone, of 

 the inner wall. The wood partition is here 

 omitted and a plate of lead, 2.5 cm. thick, is 

 used for the outer part of the wall. To close 

 the copper tube lead plugs were made, one of 

 which is solid, a second has a single opening, 

 1.5 cm. diameter, and the third has two open- 



