ERRATA. 



P. 25, line 12, for "p. 29" read' 1 p. 27." 



P. 53, line 23, for " p. 36 " read " p. 35." 



P. 233, under illustration, for "convolution" razof " convolutions." 



P. 249, line il,fot " 600 gallons " read " 400 gallons." 



