72 



THE FOOD OF PLANTS 



paper and rule it into squares, marking each square as 

 shown in the text, and placing the corresponding weight 

 in it 



Supposing our weights to have been so arranged and 

 the weighing completed, before removing the weights 

 from the balance pan examine the box and the diagram, 

 and find the weight of the object by noting the weights 

 missing. For instance, we notice that 30 grammes, 5 

 grammes, 2 grammes, '5 gramme, '2 gramme, '1 gramme, 

 05 gramme, '002 gramme are missing. Write these 

 down in the following way and add : 



30-000 

 5-000 

 2-000 



500 



200 



100 



050 



002 



37-852 grammes. 



Next remove the weights from the pan, noting down the 

 value of each as you return it to the box. On adding 

 these up they should also come to 37-852 grammes. In 

 this way a double check is obtained and mistakes in 

 weighing are avoided. 



