continually determines me to finish this voyage with Sir Humphry Davy. But if I wish to enjoy those advantages, I have to sacrifice much; and though those sacrifices are such as an humble man would not feel, yet I cannot quietly make them. Travelling, too, I find, is almost inconsistent with religion (I mean modern travelling), and I am yet so old-fashioned as to remember strongly (I hope perfectly) my youthful education; and upon the whole, _malgré_ the advantages of travelling, it is not impossible but that you may see me at your door when you expect a letter. You will perceive, dear B., that I do not wish you hastily to leave your present situation, because I think that a hasty change will only make things worse. You will naturally compare your situation with others you see around you, and by this comparison your own will appear more sad, whilst the others seem brighter than in truth they are; for, like the two poles of a battery, the ideas of each will become exalted by approaching them. But I leave you, dear friend, to act in this case as your judgment may direct, hoping always for the best. * * * * * Sir Humphry works often on iodine, and has lately been making experiments on the prismatic spectrum at M. Pictet’s. They are not yet perfected, but from the use of very delicate air thermometers, it appears that the rays producing most heat are certainly out of the spectrum and beyond the red rays. Our time has been employed lately in fishing and shooting; and many a quail has been killed in the plains of Geneva, and many a trout and grayling have been pulled out of the Rhone. * * * * * I need not say, dear Ben, how perfectly I am yours, M. FARADAY. [Sidenote: ARISTOCRATIC HAUTEUR.]