WA *TAGI 1:1 '.I- I I i;S 83 



Tin- -nal area of the float parallel to (lie water 



nila.e del. -iminr. the p..^ t|n(.iln>ii. llir readme,* .f 



response to slight v...M.th..n- m \%.ii. r -ugr, and the amount <i 

 ravailal'l. .1. the recording m-. ham -in. 'lite area 



..I ill. ll - .1 parallel (.. llir \%.it, i ^.. ,,,!.! !..- as Urge as possible 

 in ii|. -i to get a maximum amount ..1 li plarrmrnt. ami liencc 

 bouv 'n of an in< h of th> 



lit ..1 the ||.. 



When an in-lnim. nt i- in*talh -.1 \. r (If well, (lit- float ami 



ilh llu- iHMivanl lor.,- ,,! ll,. 



wilt .1 i. -I. ill. .!i -I ha lance or equilibrium; tli.it i. ilp- 



weight of th<* coun: ! ami haml <n it- -id- "1 ihe driv- 



ing wheel will <-|ii.il the rn:nliiiii*l weight of that p<rii 

 the Una! that i^ .l> \.- tin- \>.tt<-r -urface and the band on the 

 float side t ||i, driving pulh-x. ll n.. p..\s.-r \%.i- r.-.pnr.-d to 

 li. in num. -lit. then .1 eonliti,.n ..i ialance would always 



lie r,lahli^hel i mm. 1 1.1 t'l \ alter an\ li.tn-.- m tli.- .-|.-\ .ili-.n 

 ..I the water Mill. i.e ami the dri\iii wlnel would turn an 

 .im.. mil . .jii.il t<> the rhangr in risr and fall. 



' it i^ impoihle t rnn-truet a frirtionless instrument, 

 or in -ther words, one that woul.l re.piire no power to operate, 

 it i- necessary to pro\i|e the required power. That is <lne h\ 

 disturbing the i ..1 halanee l>etwn-ii llie float and the 



terw right, menti.nird above, by an amount equal to a 

 weight -nth. i. -MI i" lri\e the recording mechanism. The 



i- due to the ii*e or fall of tin- water around the float, 

 and the instrument will not rr*pond until >ueh rise or fall of 

 the v. the Hoat forms a water eolumn of the cross-sect i 



area of the float and equal in weight to the force required on 

 the rim of the driving wheel to operate the in-tnimrnt. It will 

 readily be seen that for a given weight thr altitudr of this water 

 eolumn, (whieh i> the rise or fall of the water surface i mu>l 

 lr greater for a -mall en.-.....,-, -ti.nial ar.-.i than L-r a In--- 

 ero- --e.-tiou.il area. llenee the -ante in-trum.-nt will IM- BMm 

 sensitive. v>ith a corresponding iiu-n-a-r in the refinement in 

 the record, when a largr float i- used than when a small one 

 is used. 



Since the area of the float parallel t. tl<.< water eontrol* the 

 sensitiveness of the it i- interesting to note the follow- 



ing comparison of thr wrig) rcular colums of water one 



