1030 OTTAVIO ZANOTTI BIANCO 



" But 



1 = ^ (1 — e sen^e) = ^ (1 — e + ecos'e) 



" is the equation to the surface, e being the ellipticity, when 

 * there is no disturbing force. 



" Hence the equation in the present case is 



1=-(1 -esente) + L-^; 



r = a (1 — e sen® 0) -[- L, as ^ = — g- 



" Let ^l be the angle through which the normal to the surface 

 " is thrown backwards. Now the tangent of the angle between r 

 " and the normal 



1 dr r^ n , 1 dh 1 dL 



" and ds = rdQ = adQ being an element of the are of the sur- 

 " face, the Elevation of the surface of the sea in passing north- 

 " wards = j v|i(^s = L, between the liraits X=0 and X=17 « (1). 



Quindi, servendosi di calcoli precedenti, ottiene il valore 

 numerico di L, e finalmente quello dell'elevazione del livello 

 del mare a Karachi sopra quello del capo Comorin. 



Nel 1860 apparve la prima edizione del libro di Pratt 

 A treatise on oMradions, Laplace's functìons, and the Figure of 

 the Earth; a pagine 108-109 troviamo il passo seguente, piti 

 generale : 



" Pkop. To find the effect of a small disturbing force pa- 

 " rallel to the meridian in changing the Level of the Sea. 



" 106. Let U be the disturbing force and du an element 



(1) Dipendenti dalle condizioni geoorafiche del ijroblema. 



