Standard Temperature and Level. 17 



will be the logarithm of the pressure required, at the standard 

 temperature of 32° Fahr. — Example : 



h = 29-500 inches ; T = 60° ; t = 59° ; « = 500 feet. 



For formulae Nos. 1 and 2. — If we prefer to reduce the ob- 

 served pressure in the first instance to its value at 32° Fahr. 

 the process of calculation vi'ill be as foUov/s : 



•D 17 1 XT 1 60 - 32 X 29-5 826 ^^„^ 



By Formula No. 1. — lY^TTeF" = nisi = " '0739 



h = 29-5000 

 A' = 29-4261 



Entering the first column of the table with the mean tem- 

 perature, take the corresponding number in the last column, 

 which multiply by the altitude. Divide the product by 1000, 

 and add the quotient to the logarithm of the pressure at 32° 

 Fahr.— Example : -015601 



X 500 

 TpVg T7^8005 

 + 0-0078005 

 log. of 29-4261 = 1-4687327 

 log. of 29-959 = 1-4765332 



The elevation of the barometer, when placed in the vicinity 

 of the sea, may be readily ascertained by levelling, trigonome- 

 trically, or by the portable barometer. When the situation is 

 inland, its height relative to the nearest canal, mountain, or 

 other object of which the absolute elevation has been well de- 

 termined, may be obtained by one or other of the methods 

 above mentioned. As a last resource, — extract from the diffe- 

 rent scientific journals the annual 7nea7i pressures furnished by 

 barometers placed at give7i elevations above the sea in the vi- 

 cinity of the observer, which data, in addition to the annual 

 mean heiglit of his own instrument, will enable him to ascer- 

 tain on calculation the required difference of level. 

 I have the honour to be, &c. 



Leeds, Dec, 5, 1826. J. Nixon. 



New Series. Vol. 1. No. 1. Jan. 1827. D Tabic. 



