THE ERRORS OF PRECISION. 



We refer to the habit of calculating decimals beyond the 

 limit of actual precision, and to the use of auxiliary data 

 which are not true. 



Suppose I can distinguish only the fiftieth of an inch, by 

 sight, can I then pretend to accurately measure to the 

 thousandths? And again, if I weigh to the centigramme 

 because my balance requires at least half a centigramme of 

 overweight to turn distinctly, how can I pretend to know 

 the tenth of a milligramme by weighing with that balance? 



And if, for calculating the cost of a given number of 

 things, I use a false value per unit, will not my calculated 

 price be false also, and therefore worthless? 



We shall see, that also this kind of error is constantly 

 committed by chemists, in their " adopting" as true some 

 determination made by men in authority, without exacting 

 proper proof that the authority did commit no error in his 

 work. 



Our Course of Training. 



When we shall have become familiar with the reality of 

 these errors, and shall have learnt how universally these 

 very errors have been and are being committed by chemists 

 in atomic weight determinations, we will have completed 

 that introductory course of training necessary to the begin- 

 ning of the study of the chemical and simple mathematical 

 methods that must be used to obtain the true and absolute 

 atomic weights of the chemical elements. 



We shall now present each of these common methods 

 and their common errors in the simplest way possible, by 

 actual examples, and with the necessary details. 



In order that this preliminary work may not become too 

 tiresome, we shall freely call spade a spade, independent of 

 the hand that uses it. 



Our object being to establish truth, we shall not com- 

 promise with error, even if that error be practiced by men 

 in the highest stations. 



