Dear Darwin,

You need not make any apology for troubling me, as you call it, by helping you in your investigation of the subject of mould. I have great pleasure in doing it.²

My Son Arthur has endeavoured to shade the map so as to represent the slope of the ground from the field B. towards the “Old wall” &. the Blacksmiths shop; and it should have been down to the River.³

I cannot tell how many feet the upper part of the field is higher than the lower, but I think I could form a guess by going over again.

It is very singular, as you say, that in all the 3 pits at the top of the field B—an obstruction was found at 9 or 10 inches, whilst at the bottom of the same field the mould was deeper. The best way to decide the matter will be for us to dig a few more holes at the very top of the field B, & see if the mould always rests upon stony obstruction, or if we find it exceed 9 inches when there