SYSTEM OF MEASUREMENT A 

 \ CATION 



\- is usual in scientific works, the metric system 

 has boon adopted here. The measures of length 

 and weight may he assumed to he familiar. The 

 "dyne" is the unit of farce* and is the 961st part 

 of a gramme, The "erg** is the unit of work, and 

 is the work invoked in proceeding against a force of 

 1 dyne through the distance of 1 em. Thus, 981 

 ergs are expended in lifting 1 gramme through 1 



The exponential notation k the only 

 suitahle for the work in this hook. The 

 "exponent** indicates how many times we must 

 multiply i he number hy itself. When the number 

 is 10. it indicates the number of ciphers in the result, 

 Thus 10 100; 10*- 1,000,000. Two such- powers" 

 of 10 are multiplied hy simply adding their indices ; 



The negative index implies a reciprocal value, 

 Thus 10^- or 001. In this case, the index 



