52 
ME. W. SPOTTISWOODE ON THE CONTACT OF CIJEVES. 
+'?;DDiW 
uJy^w + wDDjW = -- {n— 
+yDDi?; +^DDiW = 
yDv •—x'DiV =xD2W—zDw = — {n—l) vw, 
—wTyD^u=. J) {{n—l)~^yzH.] —{n—iy^vyH^ 
wDDiW— wDDj'y = 'D{{n—l)~^yzH.]—{n—l)~^wzK, 
zD^u — 2/D2W =— (w— 1)"V, 
D vDiv = — {n^ 1 )- VH ^ — vtv9i, 
Di’D’i(;-D?yD==u=(w-l)-v|D?y^-D^;~-aHj, 
f -D»^=(«-l)-{3(»-2)gH-*(a ^+® ^+6 }, 
whence 
Dt.D=»-D,.D’»=(«-l)-v{(^>-l) aH-„-^(a ^+(g f- 
to which many others might be added. 
