412 



SCIENCE 



[N. S. Vol. L. No. 1296 



writers, especially the English, use this same 

 symbol for the gradient wind. So too with '^. 

 In astronomy it indicates longitude, in phys- 

 ics, wave-length; but some recent writers on 

 meteorology and aeronautics use it for lati- 

 tude. 



Again, in tracing the development of a 

 formula, one will meet for atmospheric 

 pressure, p, b, P, B, h and H used indis- 

 criminately; V for volume, velocity or radia- 

 tion; s may be space or seconds; t time or 

 temperature; and R may be a gas constant or 

 the radius of the earth. 



We therefore venture to make the start by 

 proposing the following which it is thought 

 conform to the best and latest usage. 



(p = latitude. 



X = longitude. 



7r = 3.1416. 



e =3 base nat. logs. 2.718. 



w = angular velocity of earth's rotation. 



= 2ir/86,164 sec. = .00007292. 

 K = ratio of specific heats, constant pressure to 



constant volume. 

 K^ = k for air = .2375/.1683 == 1.41. 



fc for water vapor = .4734/.3631 = 1.30. 

 Cj,^ ^ specific heat dry air at constant pressure, 



in heat units .2375. 

 C„ , ^ specific heat dry air at present volume, in 

 heat units .1683. 

 Cp^ specific heat dry air at constant pressure 



in grav. force 9935787. 

 C» = specific heat dry air at constant volume in 



grav. force 7065453. 

 p = density, 

 pi = density of water at standard conditions 



p..=z density of dry air at pressure 1,000 kilo- 

 bars and temperature, 1,000 kilograd 

 1,276 g-ms./cu. m. 

 Pa = density of water vapor pressure 1,000 kilo- 

 grad =5 gms./cu. m. 

 go == acceleration due to gravity at 45 latitude 

 and sea-level, 980.615 cm./sec^. 

 : gravity potential = go/lfiOOz. 



gv 

 clgo 



= normal gravity decrease with altitude = 



.0003086 dynes/meter. 

 = bar or unit of pressure expressed in force 



= 1 dyne/cm.2. 

 = kilobar or 1,000 bars, the pressure unit 



commonly used. 



mi = millibar or 1/1,000 bar. 

 mgb = megabar or one million bars. This pres- 

 sure is an absolute atmosphere of .987 

 of the old sea-level atmosphere. It is 

 the pressure given by 750.1 mm. of mer- 

 cury (29.53 inches). 

 One megabar atmosphere acting through 

 one cubic centimeter does one megerg 

 of work. 

 1/A = mechanical equivalent of heat i^ 42683. 

 ^oM = gravity work of heat = 41,851,000 ergs. 



A = heat equivalent of work = .000023. 

 A/go = heat equivalent of gravity work = 

 .000000023. 

 ■y = volume; mis = mass; 2 = length; vel.= 

 velocity; «== vertical distance; p = 

 pressure. 

 )• = radius ; s = second ; m = meter ; m/s = 



meters per second. 

 B 7=z gas constant, which is nat a constant in 

 the atmosphere, for there is circulation 

 and gain or loss of heat. The student 

 should question all equations in atmos- 

 pherics in which it is assumed that the 

 gas coefficient is a constant. 

 B = 2,870,000 if pressure is in bars. 

 Tp = temperature on the Fahrenheit scale. 



Freezing 32°; boiling 212°. 

 T c^ temperature on the Centigrade scale. 



Freezing 0°; boiling 100°. 

 T A= temperature on the Absolute Centigrade. 



Freezing 273°; boiling 373°. 

 Tf^ =■ temperature on the Kilograd. Freezing 

 1,000°; boiling 1,366°. 

 ■Ratio of scales: 1 degree F. c=2.04 K. 

 1 degree C. = 3.66 K. 

 1 degree K. = 0.491 F. 

 1 degree K. = 0.273 C. 

 a = radiation constant = 5.7 X IQ-ia. 

 N = Avogadro constant = 6.06 X lO'^s. 

 7io = number of gas molecules per cu. em. at 

 1,000 kbs. pressure and 1,000K. tempera- 

 ture =2.705 X 1019. 

 7)ift=mass of hydrogen atom = 1.662 X 10"2*. 

 ei = electron = 4.774 X 10-i». 

 Q=heat energy; Tr = external work; U = 

 inner energy. 

 r(;3= earth's radius at equator ^ 6,378,388 

 meters (3,963 miles). 



Alexander MoAdds, 

 George P. Payne 

 Blue Hill Observatoet, 

 October 18, 1919 



