In the account of Lincoln Castle, lately read to the Society by Mr. King, I find that a singularity in one of the towers had escaped the notice of that excellent and most accurate observer, who, having viewed the castle from within, had not seen a most remarkable arch opening into the ditch from the lower part of the said tower, which is marked by the letter (i) in fig. XXVI. of his drawings, and mentioned in page 265 of the letter press.