From Edward Forbes 6 May 1851

Dear Professor Henslow

I do not know how to apologise to you for my unconscionable detention of your M.S. but must even crave your pardon to admit that I mislaid it. It has now however come to light again. In my mind it is an excellent document & your plan one to which I fully assent.

In it, I would object to the sense in which you use the word pleistocene - as hitherto used has been synonymous with the epoch of the northern drift.

In your printed paper you use the term "Miocene period" to signify both the Red & the Coralline crag epochs. Lyell has given up this view of the crag ages, in his new edition of the elements, after a long sit over the matter with myself & Searles Wood. The Red Crag seems to me to be the immediate commencement of the drift epoch & the Coralline crag to be pliocene (or older pliocene if you like - using "newer pliocene & pleistocene" as synonymous.

The Bordeaux Beds are however truly miocene.

At the end of my paper on the "Origin of the British Fauna & Flora" I have ventured on a view of the relative ages of our tertiary epochs, to which I still adhere, with the exception of regarding the Coralline crag as "miocene" which when that paper was written I maintained without many doubts but gave way to Lyell's then opinion.

ever very truly Yrs

Edward Forbes