6 INTR OD UCTION. 



10. How to Learn the Metric System. According to our expe- 

 rience, there are three chief requisites : 



11. 1. Absolute certainty of the significance of gram, liter and meter, 

 as the units of measure of weight, capacity and kngth, respectively. 



With the child or unlearned person, this may be purely an effort of memory. But 

 most persons can save something by connecting gram with gravity, liter with liquid, and 

 meter with measure, or with the word itself as it occurs in thermometer, barometer, etc. 



12. 2. Certainty of the force of the prefixes. 



With the child, this too is a matter of memory. But the prefixes of the names of the 

 divisions are from the Latin, while those of the multiples are from the Greek. Since Greek 

 increases while Latin diminishes, it has been proposed to combine the initials of the four 

 words in a single mnemonic word gild. We suggest, instead, that the gr. of Gh'eek be asso- 

 ciated with the same letters in greater, and that Latin and less have the same initial. 



Deci, centi, and mitte are familiar to most persons in the words decimate, centipede 

 and millipede, while deka, hekto and kilo, are known to some in decade, decalogue, heka- 

 tomb, and chttind. Of these six prefixes, however, centi, mitti and kilo, are much more 

 often used than the others. 



13. 3. Personal familiarity with some metric measure. 



The shortest and surest way to a knowledge of the metric system is to carry some 

 metric measure, or have one always at hand. The five-cent nickel piece is 2 centimeters 

 in diameter, and weighs 5 grams. The student is advised to carry a metric rule in the 

 pocket, and to keep another always upon the table. 



The prices of Rules and Tapes vary from 3 cents to as many dollars. A list of the 

 styles and prices may be obtained from the American Metric Bureau (A), and from dealers 

 in such articles. 



FIG. L 



FIG. 1. A section, about one tenth, of the paper meter-yard, furnished for 20 cents 

 by the American Metric Bureau (A, No. 26, 410). The face has the meter and the yard 

 side by side, and the back bears a complete Table of metric and English equivalents, 

 embracing 198 separate entries. The whole folds into the length of a decimeter, so as to 

 be easily carried in the pocket, and the Table may be consulted without unfolding the 

 paper. " Moisture affects the absolute length, but not the accuracy of comparison." 



