ACCOUNT OF WR. BANKS S INSTRUMENTS, 79 



Account of the Sifnaiinyi of the Instruments employed by 

 Mr. Robert Banks, ^br the MeteorologicalJouriial. 



JL HE barometer, the lieigbt of which is registered every Barometer, 

 day at 9 A, M., is placed at the height of 27 feet from the 

 ground. Now we learn from Dr. Young, that the Thames Calculation of 

 at Buckingham stairs, 15f feet below the pavement in the ^^^ height 

 left hand arcade, is 43 feet above the level of the sea, by 

 barometrical comparison with the Seine ond tthe Mediterra- 

 nean. But he observes, that this calculation probably gives 

 the height too great. Mr. Brindley, levelling from Boul- 

 ter's Lock to Mortlake, by order of the City of London, in 

 the year 1770, found the fall upon 41 miles to be 75| feet. 

 On the last 8 miles of this distance, however, the fall was 

 only 1^2 feet. Now if we allow the fall from Buckingham 

 stairs to the Lower Hope to average only 1 foot per mile, 

 the difference of level will be at least 35 feet. This, added 

 to 42 feet, the height of the ground where Mr. Banks's 

 bouse stands above the Thames at Buckingham stairs, and 

 27 feet, the height of the barometer above the ground, we 

 shall have 104 feet for the height of the barometer above 104 feet, 

 the level of the sea. 



The thermometers hang 5 feet from the ground, against Therm&metere, 

 a wall that has nearly an eastern aspect, and is completely 

 sheltered from the sun both at its back and front the whole 

 day, in such a manner that it cannot be affected by its heat, 

 either direct or reflected. Five are generally employed for 

 the purpose, because it is well known, if the bulbs be not 

 of the same size, they are subject to vary a little when the 

 temperature is taken at any stated hour, some rising or fall- 

 ing more quickly than others from .this circumstance, though 

 a little sooner or later they would indicate the same height. 

 For this reason a mean of them is taken. 



Under the head of weather, if any rain have fallen during Weathw. 

 the day, the word rain is inserted in the day column. The 

 weather in the night column is noted about eleven o'clock, 

 P.M., at which time, if any I'ain fall, rain is set down; if 

 it do not rain, yet no stars are to be seen, the word cloudy 

 is inserted ; when there is no rain, and a greater or less num- 

 ber of stars; are visible, it is marked as fair* 



