— 170 — 
a'b" = ih — rm = l( 1 4-/3 0), 
a'c — l'(\ 4- /3 0), 
af = rf" = a'c — cz = Z'(l 4 - j3 0) — 1' == Z'/ 3 
pm = e&" = dilatazione di ce, ossia di l — Z'j dunque = (Z • — Z') /3 0, 
hi = Z (14— oc 0), , 
hk = ki — ih — l (Ì-+- <x 9) — ili = Z (1-t- a 0)— a'Z>'' — 
= l (1 4- a — l (1 4- /3 0) = Z (a — (3) 0 
np = mn — pm = a.Z (a — /3) 0 — (Z - Z') fi 0, 
nq — ik = l(\-+- « 0), 
mq = nq 4- mn = Z (1-4- a 0 ) 4- a.Z (a - /3)0, 
qr = mq — mr = l (Ih- a 0) - 4 - a.l (oc - /3) 0 — ih — 
— Z ( 1 4 - a 0) 4 - a.Z ( 0 : — /3) 0 Z (1 4 — ®), 
= Z (1-4-a) (a — /3)0, 
l'f 
qr —b qr= b. I ( 1 4- a) (a — /3) k 0, 
f's — a"s — a"f' = òZ (1 4 - a) (a — /3) 0 — af — 
— bl (l-t- a) (a — /3) 0 — Z'/3 0, 
ccx' = f's 4 - la dilatazione di fx, dunque = 
= bl(l-t-a)(«—p)9 — l'p 0 4 - Z"y 0 . 
Stabilito, mediante quest’ultima formula, quanto si abbassa il fondo xy del 
