From Thomas Rivers   30 January 1863

My dear Sir/

I am now going to pester you with a question.¹ In the cultivation of peach trees in enclosed houses I have found that they cannot be kept in health unless the fresh air is admitted so that it enters at a lower level & makes its way under the leaves as at a

Mem the lines are to be supposed the two walls of a house

rising as it becomes rarefied by the heat of the house, & that air admitted at the upper part of the wall of a glass roofed house as at b will not keep peach trees in health   this has induce⁠⟨⁠d⁠⟩⁠ me to think that the lungs ⁠⟨⁠of⁠⟩⁠ the leaves (so to speak) are on the under surface— there is as you know much difference in the appearance of the two surfaces. Now can you by employing a powerful microscope & your power of mind do anything for me in this matter?

Referring to my last² I was brought to my, I fear, idle reasoning on the effects of soil & climate on our race by observing for several years past English gardeners & nurserymen visiting here who had lived from seven to ten years in the United States of America some from the far west others in the sea-board states with only one exception & he was a Scotchman, I remarked that in their features & figures they had assumed the genuine American type the cheekbones in most cases high the nose thin & if in the least inclining to the aquiline this peculiarity much agravated. the cheeks hollow the eyes sunken everything belonging to them reminding one of the normal Indian race. I have often expressed my surprise to those men that soil & climate would have so changed them & they have admitted that they felt a change not only in their persons but in a rush of fierce energy unknown to us at home.

These facts are all straws but they may give a hint however trifling to your reasoning powers

I am My dear Sir | Y^rs. very truly | Th^os. Rivers