ERR A T A. 
Pago 141, line 14, for “ in Fig. 2”, read “above”. 
Plate YII., column G, line 13 of the Computation : the signs for degrees, &c., arc 
erroneously given as figures (0, 1, 11). 
Plate XIII. The numbering of Figs. 3 and 4 should be transposed. 
