CH. yil] KLINOSTAT. 173 



balance is tested. The hammering must be repeated 

 until, when the spindle is made to rotate, it has no 

 marked tendency to come to rest in one position rather 

 than another. 



The clock can be rotated in the vertical plane by 

 turning on the screw R, and thus the driving gear can be 

 tightened or slackened. When a new loop of silk has to be 

 adjusted on the wheel, or when any operation connected 

 with the experiment has to be performed, the clock should 

 always be stopped by inserting into the balance wheel one 

 end of a bit of lead wire, of which the other end rests on 

 the board b. If this precaution is neglected the loop of 

 silk may become entangled in the clock wheels, or the clock 

 may be forcibly stopped by touching one of the wheels in 

 such a way that the escapement becomes fixed ; and this 

 never happens if the balance wheel is 'stopped as above 

 described. If proper care is taken a box of earth and 

 plant weighing together 1000 grams may easily be kept 

 in constant rotation. If the apparatus seems at all top- 

 heavy a heavy weight wt may be placed on the board. 



For experiments on diaheliotropism Ranvmculua ficaria 

 is useful, as it is obtainable early in the year and grows, 

 healthily indoors. We cultivate Ficaria by wrapping the 

 roots in wet cotton-wool protected by a covering of india- 

 rubber cloth. The plants so treated are fixed by means 

 of large pins to a cork disc taking the place of the box B 

 in fig. 34. The klinostat is placed as close to the window 

 as possible, and it is desirable, though not necessary, to 

 keep extraneous light away by a black curtain hung 

 behind and at the sides of the apparatus. 



