ERRATA. 



Page 33. In the figure between S and c, put C at end of line V. 

 Page 42. In the figure at end of PS, put V. 



Page 47. line 9, for YP read YS ; and after &quot; circle,&quot; transpose, &quot; and 

 joining VF &quot; to before &quot; we.&quot; 



Page 48. line 10, add &quot;and the Fathers fall into the same error.&quot; I. 109. 



