284 
GEOGRAPHIC TABLES AND FORMULAS. 
[BULL. 214. 
CONSTANTS. 
Log. 
Basis of natural logarithms e = 2. 7182818285 0. 4342944819 
Modulus of Briggs's logarithms m = 0. 4342944819 9. 6377843113- 
Radius of the circle in seconds r = 206264. 8062 5. 3144251332 
Radius of the circle in minutes r = 3437. 74677 3. 5362738828 
Radius of the circle in degrees r = 57. 2957795 1. 7581226324 
Circumference of the circle in seconds 1296000 6. 1126050015 
Circumference of the circle in minutes 21600 4. 3344537512 
Circumference of the circle in degrees 360 2. 5563025008 
Circumference of the circle for the diameter. = 10. 0000000000 
= 3.1415926536 0.4971498727 
10 
ASTRONOMICAL CONSTANTS (HARKNESs). 
Sidereal year = 365.256 357 8 mean solar days. 
Sidereal day = 23 h 56'" 4. s 100 mean solar time. 
Mean solar day = 24 h 3 m 56. s 546 sidereal time. 
Mean distance of the earth from the sun = 92 800 000 miles. 
PHYSICAL CONSTANTS. 
Velocity of light (Harkness) = 186 337 miles per second = 299 878 km. per second. 
Velocity of sound through dry air = 1090 v^l-f-0.00367 t° C. feet per second. 
LINEAR EXPANSIONS OF PRINCIPAL. METALS IN MICRONS 
PER METRE (OR MILLIONTIIS PER UNIT LENGTH). 
Name of metal. 
Aluminum 
Brass 
Copper 
Glass 
Gold 
Iron, cast 
Iron, wrought... 
Lead 
Platinum 
Platinum-iridium 
Silver 
Steel, hard 
Steel, soft. .. 
Tin 
Zinc 
Expansion 
per 
degree C. 
Expansion 
per 
degree F. 
20 
11.1 
19 
10. 5 
17 
9.4 
9 
5.0 
15 
8.3 
11 
6.1 
12 
6.7 
28 
15.5 
9 
5.0 
8.7 
4. S 
19 
10.5 
12 
6.7 
11 
6.1 
19 
10.5 
29 
16.1 
o 
