(1) Inches = millimetres divided by 25·39954 (2) Millimetres = inches multiplied by 25·39954
Of course, a table of equivalent values should be drawn up and employed, when a large number of observations are to be converted from one scale to the other.
2. In Germany, barometers are sometimes graduated with old French inches and lines,--the vernier generally indicating the tenth of a line.
English Inches. 1 douzième, or point = 0·0074 12 points = 1 ligne = 0·0888 12 lignes = 1 pouce = 1·065765 12 pouces = 1 pied = 12·7892 1 pied = 324·7 millimetres.
"The Germans indicate inches by putting two accents after the number; lines, by putting three accents; 27" 3'''·85, means 27 inches 3 lines 85 hundredths of a line; more frequently, they give the height in lines, and the preceding number becomes 327'''·85."--_Kaemtz._
3. _Rule for finding Diameter of Bore of a Barometer Tube._
"If the maker has not taken care to measure the interior diameter directly, it may be deduced from the exterior diameter. The exterior diameter is first measured by calipers, and, by deducting from this diameter 0·1 of an inch for tubes from ·3 to ·5 of an inch in external diameter, we have an approximation to the interior diameter of the tube."--_Kaemtz._
Sea Scale. Wind. Land Scale. ---------- ----- ----------- 0 to 3 = Light = 0 to 1 3 " 5 = Moderate = 1 " 2 5 " 7 = Fresh = 2 " 3 7 " 8 = Strong = 3 " 4 8 " 10 = Heavy = 4 " 5 10 " 12 = Violent = 5 " 6
Pressure in Velocity in Pounds (Land Scale). Miles (Avoirdupois) (Hourly). ------------- --------- ----------- 1/2 = 1 = 10 5 = 2 = 32 10 = 3 = 45 21 = 4 = 65 26 = 5 = 72 32 = 6 = 80
5. Letters to Denote the State of the Weather.
_b_ denotes blue sky, whether with clear or hazy atmosphere. _c_ " cloudy, that is detached opening clouds. _d_ " drizzling rain. _f_ " fog. _h_ " hail. _l_ " lightning. _m_ " misty, or hazy so as to interrupt the view. _o_ " overcast, gloomy, dull. _p_ " passing showers. _q_ " squally. _r_ " rain. _s_ " snow. _t_ " thunder. _u_ " ugly, threatening appearance of sky. _v_ " unusual visibility of distant objects. _w_ " wet, that is dew.
A letter repeated denotes much, as _r r_, heavy rain; _f f_, dense fog; and a figure attached denotes duration in hours, as 14 _r_, 14 hours rain.