454 



ON THE TOSITION OF LEAVES "WITH EEGAED TO LIGHT. 



Fig. 17. 



of the disk d in the space sp ; and 4 centim. is in practice 

 found to be sufficient for the diameter of h h. If now the 

 screw sc is made to project through the disk and press against n, 

 the disk will be forced against the fixed plate m ; and by 

 this means the spindle can be secured in an eccentric posi- 

 tion ; and thus the centre of gravity of the box and plant can be 

 brought into the axis of rotation. This is practically managed in 

 a simple manner. The screw is loosened just enough to allow 

 the disk d to be moved by the applica- 

 tion of a little force, and yet to support 

 the weight of the box without allowing 

 any slipping to occur. The plant is 

 allowed to assume its natural position, 

 which will be with the heaviest side 

 downwards ; the box is then lifted by a 

 hand placed under it, so that the groove 

 g no longer touches the friction-roller, 

 and then the upper surface of the boss c 

 (fig. 16) is struck gently with a hammer 

 in a vertical direction. This displaces 

 the disk d slightly in the right direc- 

 tion ; the spindle is then replaced on Fig. 17.— Elevation of part of 

 the wheel, and its state of balance is the klinostafc i n the same P lane 

 again tested by giving it a slight rota- as fig. 13, showing the arrange- 

 4." •j/l xi. i t -c- ■, . •!! i ment by which a plant can be 



tion with the hand ; if it stdl has a ten- -, '., . .. . . 

 j ' fixed so that its axis is perpen- 



dency to come to rest in a particular dicu i ar to the axis of rotation 

 position, the vertical blows with the instead of parallel as in fig. 13. 

 hammer must be repeated until when B, box with flower-pot and 

 the spindle is made to rotate, it has no P lant ; *• 8 P indle i b > P ortion 

 marked tendency to come to rest in one ° f board ° n which instrument 

 position more than another. ' Btands ' *' the Bupport 



A few small points connected with the practical working of the 

 instrument may be mentioned. The clock is fixed to a wooden disk, 

 and this is fixed to the support *' by a screw E passing through 

 the disk at a point close to its circumference (see fig. 15). Thus 

 the clock can rotate in a vertical plane, and can be fixed in any 

 desired position by means of the screw. It is by this device 

 that the driving-belt of silk passing round p and wor¥ can be 

 rendered tighter or Blacker with great ease ; and a little expe- 

 rience soon shows the observer the necessary degree of tension. 

 If the spindle has been removed from its bearings, it is useful to 



