BAR 



Porto Bello - f - ff ..._. ffwj ^ 29. 80 



Liverpool fr , fffffffrf ^ ft ^ tfffMtfffJJfJM ^^ 29. 74 



Turin" - r ^ fr - JfWJWJ> ,, JWJI 29. 52 



Petersburg ^^^-^ ff ^ ff ^ 29. 57 



Gottingen ^^^^^^^^^^^^^ 29. 37 



Paris ~~~^~ 29. 31 



Basle ^^^^^^^^^^^^^^^ 28. 82 



Nuremberg ^^^^^^^^v^vv^^v^^^^ 28. 69 



Zurich 28. 29 



Clausthal 27. 89 



Chur 27. 71 



M. St Gothard ^ 23. 05 



QuitO f r rf r fTr *r JJ - ffrJJ - fJ - W fssw- JJ .-ss J .-s Ja - J 21. 37 



We shall close this article with the following Proposition : 



If a Barometer tube be in part only filled with mercury, and then its 

 open end be immersed in a basin of the same fluid, the mercury will sink 

 below the point called the standard altitude, or the point at which it 

 would have stood if no air had been left in j and the standard altitude 

 will be to the depression below that altitude, as the space occupied by the 

 air after the immersion, to the space occupied before. 



This Proposition may be applied to the solution of two problems ; for 

 we may either give the quantity of air left in before immersion, to find 

 the altitude of the mercury after immersion ; or we may give the alti- 

 tude of the mercury after immersion, to find the quantity of air left in 

 before. 



Ex. Let 5 inches of air be left in a tube of 35 inches before inversion, 

 to find the altitude of the mercury after. 



Let x depression below the standard altitude then 30 ; x ; : x .+ 5 

 C 5, .'. x - 10. 



BARS /row, to find the weight of .( Gregory. ) 



The following is an approximate rule for finding the weight of cast 

 iron bars : 



Take -rrr of the product of the breadth and thickness, each in eighths 



of an inch ; the result is the weight of one foot injength, in avoirdupois 

 pounds. 



Hence an inch square cast iron bar would require 9 feet, or 108 inches 

 in length lor cwt. For wrought iron square bars, allow 100 inches in 

 length of an inch square bar to $ cwt. 

 41 C g 



