43^ 



APPENDIX. 



FOOT-POUND. The work which will raise one pound one f ">ot high. 

 For conversion factors see page 197. i." 



FOOT-POUNDALS. The English unit of work^foot-p.\liids/g. 

 For conversion factors see page 197. 



g. The acceleration produced by gravity. 



GAUSS. A unit of intensity of magnetic field 1= i E. M. U. = 4 X lO"^" E. S. U. 



GRAM. See page 6. 



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



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



GRAVITATION CONSTANT = G in formula G "^ = 665.8 X lo-i" cm.s/gr. sec.^ 



HEAT OF THE ELECTRIC CURRENT generated in a metaUic 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) 

 74. 181 in small calories. 

 The heat in small or gram-calories per second ::= (amperes^ X ohms) /4.181 =voltsy 

 (ohms X 4.181) = (volts X amperes)/4.i8i = watts/4.181. 



HEAT. Absolute zero of heat == — -273.1° C. 



HEFNER UNIT. Photometric standard; j-^^ 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." = 10^ E. M. U. = 1/9 X lo-^^ E. S. U. 



HORSEPOWER. The English and American horsepower is defined by some author- 

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

 horsepower is defined by some authorities as "]$ kilogrammeters per second and by 

 others as 736 watts. See page 197. 



JOULE. Unit of work = 10^ ergs. For electrical Joule see p. xxxvii. 



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

 For conversion factors see page 197. 



JOULE'S EQUIVALENT. The mechanical equivalent of heat = 4.185 X 10' ergs. 

 See page 197. 



KILODYNE. 1000 dynes. About i gram. 



KINETIC ENERGY in ergs = grams X (cm./sec.)72. 



LITER. See page 6. 



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



MEGABAR. Unit of pressure = i 000 000 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. 



MHO. The unit of electrical conductivity. It is the reciprocal of the ohm. 



MICRO. A prefix indicating the millionth part. 



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

 capacity. 



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



MIL. One-thousandth of an inch. 



MILE. See pages 5, 6. 



MILE, NAUTICAL or GEOGRAPHICAL = 6080.204 feet. 



MILLI-. A prefix denoting the thousandth part. 



MONTH. 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 = 27.21222 days. 



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

 (mean 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 

 Cmean value) =; the ordinary tnonth. It varies by about 13 hours. 



