622 APPENDIX 



1 milligram = 0.001 gram = 0.0154 grain (avoirdupois). 



1 centigram = 0.01 gram = 0.1 543 grain 



1 decigram = 0.1 gram. = 1 . 5432 grain 



1 gram = 15.432 grains 



1 kilogram = 1000. grams = 2.2046 pounds. 



The following table shows the equivalents in the metric system to 

 some of the common weights and measures : 



1 inch 2 . 54 centimeters 



1 foot = 0.3048 meter 



1 yard 0.9244 meter 



1 rod 5.029 meters 



1 mile 1 . 0933 kilometers 



1 square inch 6 . 452 square centimeters 



1 square foot . 0929 square meter 



1 square yard 0.8361 square meter 



1 acre 0.4047 hectare 



1 square mile = 259. hectare 



1 cubic inch = 16 . 29 cubic centimeters 



1 liquid quart . 9465 liter 



1 liquid gallon 3 . 786 liters 



1 ounce avoirdupois = 28.35 grams 



1 pound avoirdupois = . 4536 kilogram 



1 ounce Troy = 31 . 104 grams 



1 pound Troy . 3732 kilogram 



Thermometer Scales. The principle on which thermometers are 

 constructed is the following: A fine glass tube, having a closed bulb 

 on its lower end, contains chemically pure mercury. The latter is 

 heated in a boiling, strong, salt solution. The mercury then rises in 

 the tube, evaporates partly, and expels all the air from the upper 

 open end of the tube. If now this upper end is fused and the mercury 

 allowed to cool a vacuum is formed above it, and when the mercury 

 again expands it meets with no resistance. The thermometer tube, 

 after having been sealed at the upper end, is placed in melting ice and 

 the point to which the mercury column reaches is marked the freezing 

 point of water (zero = 0). The thermometer is then immersed in boil- 

 ing distilled water and the point to which the expanded mercury now 

 reaches is marked as the boiling point of water. The space between 

 the freezing point of water and its boiling point is marked off into 

 a number of equal degrees. In the Celsius scale the space is marked 

 off into 100 equal parts, but in the Reaumur scale into 80 equal parts. 

 The thermometer scale most commonly in use in this country in every- 

 day life originated in a somewhat ridiculous manner. Fahrenheit, 

 living in northeastern Prussia, on a very cold winter day, adopted 

 the then prevailing temperature as the zero point of his scale. He 

 divided his thermometer into 212 equal degrees between his zero 

 and the boiling point of distilled water. The freezing point of water 

 on the Fahrenheit scale is situated at 32 F. There are, therefore, 

 the following rules for changing one of the three scales into another: 



1. n degrees Reaumur = n X degrees Celsius 



2. n degrees Celsius = n X * degrees Reaumur 



3. n degrees Reaumur = n X + 32 degrees Fahrenheit 



4. n degrees Celsius = n X f + 32 degrees Fahrenheit 



5. n degrees Fahrenheit = n -^ 32 X | degrees Reaumur 



6. n degrees Fahrenheit = n -f- 32 X f degrees Celsius 



