879 
aS, and as, and the integration is carried out over the areas, 
A, and Aw of the two orifices. This integral is calculated in 
the appendix, peregravh Q9.; but a may be approximated with 
sufficient accuracy by its leading term, since its value is small 
in any case. As an example one may find the effect of the cir- 
cumferential pistons on the central piston (the zero piston) in 
the Hartmann-Hilltar gauge. (See Fig. 4, and reference 5 for 
Fig, 4 details. The zero piston 
OF @ is set in center of the gauge 
S 
© ‘ ® and is surround by 6 pistons, 
all at the distance, s, from 
@) GB) it. The pistons are all of 
the same radius, R.) If the coupling (18.1) 1s included, the 
corrected equation of the zero piston of the Hartmann-Hilliar 
gauge is : : Re R2 6 
(18.2) (M* 3PpR) z* ks = 2aP,[1- $= ted a 
The sum is carried out over the masses My of the 6 circumferential 
vistons. The correction to be made in the deformation of the 
pellet is 1.4% in a tyvical case. 
Iv. THE RESPONSE OF THE BLOCK AND ITS INFLUENCE ON THE PISTONS 
19. Consider a single piston at the center of a finite circular 
baffle. (The words baffle and block sre interchangeable here. 
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