APPENDIX II 71 



Take a piece of metal, say a lead bullet or a penny, 

 see that it is clean and dry, and having lowered the 

 beam, place it on one pan of the balance. Open the 

 box of weights, and with the nippers provided for the 

 purpose lift out the heaviest weight in the box and 

 place it on the other pan. Now begin to raise the 

 beam, turning the brass stud very gently, and noting the 

 pointer. The pointer will probably move in one direction 

 as the beam is being raised. We need not therefore 

 raise the beam completely. Lower the beam, and if the 

 weight is too heavy, remove it and place on the pan the 

 next in order. If this is too light, add to it the next 

 again. If too heavy with this addition, remove the last 

 weight added and try the next. Do not try and guess at 

 the weight of an object, but go systematically through the 

 box. When you arrive at the tiny weights and are near 

 to the true weight of the object, you will have to raise 

 the beam completely and note the swings of the pointer. 

 The glass front should be closed during these final 

 observations. Having got the balance exactly in equi- 

 librium and lowered the beam, next look at the box of 

 weights. 



The brass weights beginning with 100 or 50 grammes 

 go down to 1 gramme. The fractions of a gramme are 

 of aluminium or platinum, and are tenths, hundredths, 

 and thousandths of a gramme. 



The tenths are marked '5, -2, !, 1. The hundredths 

 are marked '05, "02, -01, '01 ; the thousandths or milli- 

 grammes are merely marked 5, 2, 2, 1, their size indicating 

 their weight, or in some cases they are made of wire, 

 which is bent to show the weight thus, O V V - ; 

 the number of bends indicating the number of milli- 

 grammes. 



In the more expensive boxes each weight has its own 

 little pigeon-hole. In cheaper boxes the fractions of a 

 gramme are all mixed together. In the latter case it is 

 as well before beginning a weighing to take a piece of 



