(486) 
account the so found gross pseudo-accidental errors, has been studied and 
drafted: by the chief engineer geographe Levallois for the simultaneous com- 
pensation of a block of several strips; applied to a block of three strips of 65 
km, the following results are reached; 
in levelling, on 140 calculated points: 
number of points with errors less than 3 metres: 70 
number of points with errors between 3 and 6 m: 48 
number of points with errors more than 6 metres: — 22 
maximal error: 10 m; 
in position: values of the same order.