1865.] and Temperature in Barometric Hypsometry, c. 283 



PRACTICAL EULES WITHOUT ANY TABLES. 

 1 . English feet, Fahrenheit temperatures. 



Multiply the difference of the barometric readings in any unit by 52400, 

 and divide by the sum of the barometric readings. [If the result be 1000, 

 2000, 3000, 4000, or 5000, add 0, 0, 2, 6, 14 respectively.] 



Subtract 2 5 times the difference of the temperatures of the mercury. 

 Multiply the remainder by the result of first adding 836 to the sum of 

 the temperatures of the air, next dividing by 900, [and finally 



adding for latitude 0, 20, 30, 40, 45, 



and subtracting for lat. 90, 70, 60, 50, 45, 

 the decimals -0026, -0020, -0013, -0005, 0.] 



To this product add the height of the lower station, [and if the sum is 



5000, 10000, 15000, 20000, 25000, 

 add 1, 5, 11, 19, 30, 



subtracting the same numbers when the upper numbers are the heights of 

 the lower station.] 



The final result is the height of the upper station above the sea-level 

 according to Laplace's complete formula. [For British heights, the cor- 

 rections in brackets may be omitted.] Fresh observations should be made 

 whenever the temperature does not decrease about 4 degrees for a fall of 

 one inch in the barometer. Calculate great heights in sections. 



Ex. 4. The same data as Ex. 1, with the exception of H being the 

 interval An in the Table of the 'Abridged Gradual Method.' 



B' 20717 A 32-1 H 9875 



V 17-931 a 25-5 L 53 



836-0 

 B'+S' 38-648 



900)893-6 



B 1 b' 2-786 



+ 52400 -9929 



--0007 for lat. 53 



38-648)145986-400(3777 



+ 6 p -9922 



3754 



3783 9875 H 



+ 9922^ +8 for 13000 



-5 for 10000 



Approximative difference 1 o 7 - 4 



of level J 9t A 13632 feet. 



Since decimals of a foot are rejected, there is always a liability to a dif- 

 ference of 1 or 2 feet between this and the logarithmic method. A 

 difference of 10 feet between this result and that in Ex. 1, is due to the 

 difference in the assumed value of H. [Continued on page 288.] 



