THE READER IS REQUESTED TO MAKE THE FOLLOWING CORRECTIONS: 



PACE. LIST. 



M. 2, from foot, /or relattcn i'«iz(j relations 



16. 2, from foof, for Mix read M'it,. 



24. in {¥'), for x' y> z' read x, y, r, 



2P. C, from foot, /or »' reorf jr" 



32. 16, /or number read member 



33. in (£"), far each — read + 

 E8. in (_P"),for + E' read — E' 

 53. in (C*),for s' read z^ 



In tlie Memoir entitled "First Part of an Essay on the Theory of Systems of Rays," pnblished in the Fifteenth 

 Volnme of the Transactions of this Academy, the following additional corrections are to be made : 



2, far yf read x' 

 6, /or p 1 p J read p j p , 

 10, for Pi p read p, p^ 

 86. 1.52. 8 from bottom, after &c., insert, the functions ^, J/, 11, z, r', z'^ , &c. retaining the same forms 



as before. 

 ST. 153. in (N^), fur d.ip" read d.f" 



90. 156. 13, /or (r^) renrf(r=) 



92. 158. 2 from bottom, /or <f>" rend *"' 



dx" du'' dx" du" 



97. 163, iB(^F'),for=—^read=~°JL° 



^ ■' ■' db„ db^ - db^ rf«„ 



98. 164. 3, /or ra > 1, »«' >- 1, read m + ,:,' > 1 



5, for dm + m*^ read </"» + m'^^ 



99. 16.T. 10 from bottom, /or « read j/ 

 104. 170. in (_P^'),for sin. v read sin,* v 



