344 D E P R I N C I P 1 1 S 



et formulae differentiales hinc natae erunt : 

 (|)r:(a^-S.)(S- \(t>aT+(yz-ax){n (-).gT+(g.v-Y^)(g) 

 (|)r«T+(«^-g^) (g)k|)= l Y «-«*•) (S) |(^?^-YT+iex-Y/)(g) 

 (l")z-ST+(«>-e^-(£) 



(l^)r(«/-g«)(3 



('T,-yT+{yz-Ux){g, 





HiQG prin^a aequatio (^) + (f^)+(£^) - o induit 

 hanc formam : 



{oy-?z){i^J + {yz-ax){i:L)+(U-yj)(:'^^) 



Cui aequationi liUisfit fi T fuerit fundio quaecun- 

 que harum duarum quantitatum yx-i-^j^-\-az et 

 X X -\-jj -^- z, z nam fi ponamus 



^T :=r M (y («'^ 4- S fl>-}-a «'s) -{-Nixdx-h-jdj-^-zdz) 



erit (^-f ):zMy+Nj; (jX^nMg+Ny et (fJ-^ziMa+Ns. 



Ad alteram ergo aequationem progrcdiamur ; ac 

 primo formulam « (^ ) -h ^^ (^) -j- w (l^) euol- 

 Yamus , quae flidis fubliitutioribiis abit in 



TT {ayz-\-^yv — acLX~^^x). 



Qiiare cum T non inuoUiat tempus t ob (^) zz g 

 erit etiam {—) ~ o, Ynde fi£ 



U = T T (a y s -f- § y/ — a a x— ^ t x) 

 V zn T T (§ y ;t' -f- a §s:— y yjv — a a j) 

 W ~T T {a^j -{- a y X — '^'^ z— y y z) 



sc 



