555 



SQUARE ROOT OF THE WEIGHTS OF THE OBSERVATIONS. 



w^a^ m , w^y' m and r w-z' m , which are derived from the absolute terms for 1845 

 and 1880, are given in the tables. 



The following is the type of these equations : 



X'? w*g? + X' wig + &c. = w* x' m , 

 with similar equations for Y and Z. 



702 



