Holbrook's thoughtful sympathy, and as the following letter connects itself with the winter evening talks by the "Hollow Tree" fireside, and was suggested by them, it may be given here, though in date it is a little in advance of the present chapter. TO MRS. HOLBROOK. CAMBRIDGE, July, 1852. . . .I am again working at the human races, and have opened another line of investigation in that direction. The method followed by former investigators does not seem to me to have been altogether the best, since there is so little agreement between them. The difficulty has, no doubt, arisen on one side from the circumstance that the inquirer sought for evidence of the unity of all races, expecting the result to agree with the prevailing interpretation of Genesis; and on the other from too zoological a point of view in weighing the differences observed. Again, both have almost set aside all evidence not directly derived from the examination of the races themselves. It has occurred to me that as a preliminary inquiry we ought to consider the propriety of applying to man the same rules as to animals, examining the limits within which they obtain, and paying due attention to all circumstances bearing upon the differences observed among men, from whatever quarter in the study of nature they may be gathered. What do the monkeys say to this? or, rather, what have they to tell in reference to it? There are among them as great, and, indeed, even greater, differences than among men, for they are acknowledged to constitute different genera, and are referred to many, indeed to more than a hundred, species; but they are the nearest approach to the human family, and we may at least derive some hints from them. How much mixture there is among these species, if any, is not at all ascertained; indeed, we have not the least information respecting their intercourse; but one point is certain,--zoologists agree as little among themselves respecting the limits of these species as they do respecting the affinities of the races of men. What some consider as distinct species, others consider as mere varieties, and these varieties or species differ in particulars neither more constant nor more important than those which distinguish the human races. The fact that they are arranged in different genera, species, and varieties does not lessen the value of the comparison; for the point in question is just to know whether nations, races, and what have also been called families of men, such as the Indo-Germanic, the Semitic, etc., do not in reality correspond to the families, genera, and species of monkeys. Now the first great subdivisions among the true monkeys (excluding Makis and Arctopitheci) are founded upon the form of the nose, those of the new world having a broad partition between the nostrils, while those of the old world have it narrow. How curious that this fact, which has been known to naturalists for half a century, as presenting a leading feature