Dear Sir:

I think you will pardon me the liberty, herewith taken, of imposing this long note upon you, on the broad principle that intelligent Scientists never reject trifling ideas or suggestions.

The pleasure I experienced, this last week, in perusing your work: “The Descent of Man”, was heightened by your reviving, in my mind, an old idea in relation to the effect of the sun’s rays, through color, upon tender and delicate birds.

Permit me to quote an item, from the works of my distinguished countryman, D^r. Franklin. His experiment is undoubtedly known to you, being recorded in the Works of Benjⁿ. Franklin by Jared Sparks¹— (10 Vols.)— Vol. 6— Page 237:

“My experiment is this. I took a number of little square pieces of broad-cloth from a tailor’s pattern card, of various colors. There were black, deep-blue, lighter-blue, green, purple, red, yellow, white, and other colors, or shades of colors. I laid them all out upon the snow, in a bright sunshiny morning. In a few hours (I cannot now be exact as to time) the black being warmed most by the sun, was sunk so low as to be below the stroke of the sun’s rays; the dark blue almost as low, the lighter blue not quite so much as the dark, the other colors less as they were lighter; and the quite white remained on the surface of the snow, not having entered it at all. x x x x. It is the same before a fire; the heat of which sooner penetrates black stockings than white ones, and so it is apt sooner to burn a man’s shins. Also beer much sooner warms in a black mug set before the fire, than in a white one, or in a bright silver tankard. x x x x. What signifies philosophy that does not apply to some use? May we not learn from hence, that black clothes are not so fit to wear in a hot, sunny climate or season, as white ones; because in such clothes the body is more heated by the sun when we walk abroad, and are at the same time heated by the exercise, which double heat is apt to bring on putrid, dangerous fevers. That soldiers and seamen who must march and labor in the sun, should in the East or West Indies, have an uniform of white. That summer hats, for men or women, should be white, as repelling the heat which gives headache to many, and to some the fatal stroke that the French call “coup de soliel”—”² &c. &c. &c.

I now quote from your “Descent of Man”— Vol. 2— Page 218— (Appleton’s Edition)’³ As the latter breeds on the “barren-grounds”, when not covered with snow, and as it migrates southward during the winter, there is no reason to suppose that its snow-white adult plumage serves as a protection.⁴ In the case of the Anastomus oscitans previously alluded to, we have still better evidence that the white plumage is a nuptial character, for it is developed only during the summer; the young in their immature state, and the adults in their winter dress, being gray and black”.⁵

The thought naturally arises: that a bird being black in snow-clad regions, and changing to white on its migration to a hot climate—it would seem that Nature here takes cognizance of the power of color in drawing or attracting heat. For how could the black-feathered bird, accustomed to a cold climate, bear the heat of the sun, unless receiving from Nature a white feathery umbrella to shed the sun’s heat, in the hot climate to which it migrates?

Color may be considered from another standpoint—that of light and darkness. White admits light. Black shuts it out. White is translucent. Black is opaque. Our phrenologists (Mess. Fowler & Wells)⁶ advised me not to wear dark-colored clothes, because my vocation being sedentary, my body craved light—and when I went abroad into the sunlight, dark clothes shut out the light from my skin. They illustrated the idea by two tents: one of black-cloth—the other of white. In the white tent, a man could see to read— in the black one, he could not. They evidenced it by a laboring man, seen in bathing, whose skin all over the body, was nearly nut-brown, excepting two narrow-crossed-lines on his back and shoulders, where dark-colored suspenders had shut out the sun’s rays, and kept the skin beneath them white.

It may be that, with your close investigation of the whole subject, you have fully considered, and finally rejected the idea, that color of plumage is governed in the least by climate or seasons. But if the idea has escaped you, it certainly seems good that it should be placed under your critical analysis.⁷

Allow me one other observation, at which you may be amused: In the instances related of the retriever & ducks, and the retriever & partridges (Vol. 1— Page 46—of the “Descent of Man”) we should, I think, here in America, consider the latter retriever more intellectual than the former.⁸ Our national trait is to invent labor-saving machines; and the highest point is reached by him who accomplishes most, with the least work. As regards any respect for the bird’s life, the dog would follow his prototype master.

So we should be apt to award the premium to the retriever who intellectually planned a mode to bring both birds, without going the ground twice over.

It seems to me that Colonel Hutchinson’s retriever possessed a larger inventive brain (Mr. Pope’s criterion of human genius) than did Mr. Colquhoun’s.⁹

I remain, dear Sir, | Respectfully Yours, | Daniel F. Tyler