Researches on the Discharge of the Electric Org-an. 9: 



electricall,y-li Gated resistance are immersed. Outside of this comes 

 a layer of ice, and the whole is protected from external heat by 

 an air jacket. The thermostat works well for G — 7 hours without 

 any fresh supply of ice. 



Next we sliall describe the construction of a shutter designed 

 hy the author (Plato IL). The function of this shutter is as 

 follows. (a) When a certain place on tlie film just comes to 

 receive light from the oscillograph, the shutter opens, (b) then the 

 stimulation-apparatus is set in work, whereby the organ is excited 

 and the oscillograpl i prints tlie motion due to the ^stimulation 

 und the discliarge current, and (c) when tlie drum has made just 

 one revolution after tlie shutter first opened, it is made to close 

 so as to protect the film from unnecessary exposure to light. 

 The operations a and c are accomplislied by sending to tlie 

 electro-magnets mi the sluitter instantaneous breaks of current, 

 wliicli occur once in eacli revolution of tlie registering drum. Fig. 

 4 in Plate IV. repi'esents the construction of the shutter. It consists 

 essentially of twe) almost identical aluminium sectors A and B, 

 placed one lieliind the other witli a circular hole in eacli of them, 

 and two electro-magnets A' and />'. one fcir each sector. When 

 the sectors, by means of cords, are pulled to the left against 

 the action of the springs, and there held in position liy the 

 detents attached to the armatures of the electro-magnets, tlie shutter: 

 is ready for action. When the current is broken for an instant,, 

 at the break-circuit contrivance attaclied to the shaft above 

 mentioned, only the electro-magnet A' ])elonging to the front sector 

 is put into action and the sector A is released and turns to the 

 right, and then a free passage of light tlirough the shutter is. 

 admitted, (operation a). I>y a simple mechanism attached to 

 the front sector, the electric connection is changed automatically, 

 without interrupting the current in the operation, so that at the, 

 next break of the current, which takes place after one revolution 

 of the drum, the back sector is released and the passage of light is 

 intercepted (operation c). The contrivances for these operations 

 are illustrated diagrammatically in Fig. 2. The mechanism of 

 the operation b will be described under the paragraph of the. 



