MOVEMENTS OF IRRITATION. 457 



which is led through a glass case containing moist air, and whose 

 extreme end, outside the case, is then supported by the stand with 

 the friction rollers. 



If it is required to rotate the objects about a vertical axis, the 

 clinostat must be arranged in a different manner, since the driving 

 apparatus is not movable. 



Fig. 152 shows the clinostat arranged with the axis of rotation 

 vertical. A bevel wheel is put on one of the spindles ., 6, 

 r, the teeth of which gear into those of a second bevel wheel. 

 The latter can be fixed in any desired position on a vertical shaft, 

 w, which rests on a steel bed, carries at the top a flat brass disc, 

 and by means of a set screw, r, can very quickly be clamped to 

 the driving apparatus. 



The rates of rotation of the three spindles are different, and so 

 arranged that without loading, and with the axis of rotation 

 horizontal, one revolution of a is made in ten minutes, of b in 

 fifteen minutes, and of c in twenty minutes. But if it is re- 

 quired, greater rapidity may be secured by closing the fan. 



The clockwork requires winding up every twenty to twenty-one 

 hours. 



The advantages of the clinostat are as follows : 



(1) In rotation all possibility of shocks is eliminated, so that 

 a perfectly even movement of the objects is rendered possible. 



(2) It is very convenient for transport, and can hence be set 

 up on any work-table. 



(3) Since the clockwork is almost noiseless in its movement, 

 the apparatus is suitable even for lecture demonstrations. 



(4) The manipulation is exceedingly simple. The material for 

 observation can in the course of one to two minutes be mounted, 

 attached to the apparatus, and set in movement. The removal 

 of the objects is effected just as simply. 



(5) The strength is ample for ordinary experiments. Tests 

 showed that with the axis of rotation horizontal (as represented 

 in Fig. 148), and with a load of 2 kg., the movement was still 

 perfectly smooth and regular, though certainly it was retarded by 

 one minute per revolution. With the axis vertical, however (as 

 represented in Fig. 152), a load of 5 kg. could be employed with- 

 out retarding the rotation. 



(6) The price of the apparatus, including accessories, is 200 

 marks. 



In order to obtain a general idea of the efficiency of our appar- 



