3, 4] 



Directions for Weighing 



cardboard should be marked off as in fig. 2, each square being 

 covered with the weight whose value is written upon it. 



3. The rider is a piece of wire bent so that it may be 

 placed on the graduated beam of the balance as shown in 



Fig. 2.- Card. 



Fig. 3.— Rider. 



%• 3- 

 (•OOl). 



Each division of the beam corresponds to a milligram 

 The use of the rider, therefore, obviates the troublesome 



work of using very small platinum weights. 



DIRECTIONS FOR WEIGHING 



4. A few minutes' instruction from a teacher will be found 

 more valuable than written advice. The following rules will, 

 however, be of use : 



(a) See that the scale pans are free from dust. If not, 

 cleanse them with a large camel's-hair brush. 



(b) Always test the balance before using by releasing the 

 beam and allowing it to swing. The swings, as indicated by 

 the pointer, should be equal in each direction. If the balance 

 be not accurate, it must be adjusted. 



The two most common attachments for effecting this adjustment are : 



1. A small lever at the centre of the beam, which may be bent over 

 towards the pan which is too light. 



2. A nut running on a finely threaded screw at the end of the beam, 

 which may be screwed towards, or away from, the centre as required. 



(c) Place the substance to be weighed on the left-hand 

 pan, reserving the right-hand pan for the weights. 



(d) Always add the weights systematically in the order in 



