APPENDIX. 



FOOT-POUND. The work which will raise one pound one foot high. 



For conversion factors see page 197. 

 FOOT-POUNDALS. The English unit of work = f oot-pounds/g. 



For conversion factors see page 197. 

 g. The acceleration produced by gravity. 



GAUSS. A unit of intensity of magnetic field = I E. M. U. = J X i<r 10 E. S. U. 

 GRAM. See page 6. 



GRAM-CENTIMETER. The gravitation unit of work = g. ergs. 

 GRAM-MOLECULE = x grams where x = molecular weight of substance. 

 GRAVITATION CONSTANT = G in formula G ^-p 8 = 666.07 X icr 10 cm. 3 /gr. sec, 1 



HEAT OF THE ELECTRIC CURRENT generated in a metallic circuit without self- 

 induction is proportional to the quantity of electricity which has passed in coulombs 

 multiplied by the fall of potential in volts, or is equal to (coulombs X volts)/4.i8i in 

 small calories. 



The heat in small or gram-calories per second = (amperes 2 X ohms) /4.i8i = volts 2 / 

 (ohms X 4-iSi) = (volts X amperes)/4.i8i = watts/4.i8i. 



HEAT. Absolute zero of heat = 273.13 C, 459-6 Fahrenheit, 218.5 Reaumur 



HEFNER UNIT. Photometric standard; see page 260. 



HENRY. Unit of induction. It is " the induction in a circuit when the electromotive 

 force induced in this circuit is one international volt, while the inducing current 

 varies at the rate of one ampere per second." = io 9 E. M. U. = 1/9 X icr 11 E. S. U. 



HORSEPOWER. The English and American horsepower is defined by some authorities 

 as 746 watts and by others as 550 foot-pounds per second. The continental horse- 

 power is defined by some authorities as 736 watts and by others as 75 kilogram- 

 meters per second. See page 197. 



JOULE. Unit of work= io 7 ergs. For electrical Joule see p. xxxvii. 



Joules = (volts 2 X seconds) /ohms = watts X seconds = amperes 2 X ohms X sec. 

 For conversion factors see page 197. 



JOULE'S EQUIVALENT. The mechanical equivalent of heat = 4.i8s X IO T ergs. 

 See page 197. 



KILODYNE. looo dynes. About I gram. 



KINETIC ENERGY in ergs = gramsX (cm./sec.) 2 /2. 



LITER. See page 6. 



LUMEN. Unit of flux of light-candles divided by solid angles. 



MEGABAR. Unit of pressure = 1000000 bars = 0.987 atmospheres. 



MEGADYNE. One million dynes. About one kilogram 



METER. See page 6. 



METER CANDLE. The intensity of lumination due to standard candle distant one 

 meter. 



S'^ The Unit of electrical conductivity. It is the reciprocal of the ohm. 

 11CRO. A prefix indicating the millionth part. 



MICROFARAD. One-millionth of a farad, the ordinary measure of electrostatic 

 capacity. 



MICRON, (ft) = one-millionth of a meter. 



MIL. One-thousandth of an inch. 



MILE. See pages 5, 6. 



MILE, NAUTICAL or GEOGRAPHICAL = 6080.204 feet. 



V1ILLI-. A prefix denoting the thousandth part. 



'H. The anomalistic month = time of revolution of the moon from one perigee to 

 another = 27.55460 days. 



The nodical month = draconitic month = time of revolution from a node to the same 



node again = 27.2 1 222 days. 



The sidereal month = the time of revolution referred to the stars =27.32166 days 

 value), but varies by about three hours on account of the eccentricity of the 



orbit and perturbations." 

 The synodic month = the revolution from one new moon to another = 29.5306 days 



(mean value) =the ordinary month. It varies by about 13 hours. 



