creases or diminishes in weight. Thus, if a man or a woman weighing one hundred and fifty pounds has a brain weighing three pounds the proportion of brain-weight to body-weight is as 1:50. But, suppose the person loses fifteen pounds in weight, then the proportion becomes 1:45, whereas if there should be a gain of a like amount the proportion would change to 1:55. In the first instance, if relative weight has anything to do with intelligence the mental power would be increased, while in the other case it would be diminished. Of course, no such change takes place.
Many years ago I made several thousand observations in regard to the weight and other qualities of the brains of various species of animals belonging to the classes of reptiles, fish, birds, and mammals. In these investigations I went over to a great extent the ground previously traversed by Leuret, and in some respects made new observations. I found among other interesting facts that the brain of the canary-bird, reared in the United States, was in weight as compared to the body as 1:10·5, and in the Arctic sparrow as 1:11. These little animals have the largest brains relative to the body of any others yet examined. To pretend that they are superior in intelligence to man, in whom the weight of the brain relative to that of the body averages 1: 36·50, is, of course, ridiculous. Yet that is the conclusion to which Miss Gardener, and presumably the "twenty leading brain-anatomists," etc., would have us come.
Broca declares that the difference in weight between the brain of woman and that of man is not due alone to the smaller size of her body, but to the additional fact that woman is in the mean, when compared to man, a little less intelligent; a fact, he says, which should not be exaggerated, but which is nevertheless real. This is going somewhat farther than I have ever gone, but what Broca says in a matter of anthropology is worthy of serious attention.
When Miss Gardener says that I make relative difference "count for a great deal" when existing between two men, she passes the limits of correctness. I have never said anything of the kind.
One more point, and I have done. I stated, in the paper on "Brain-Forcing in Childhood," that the human head does not grow after the seventh year, and Miss Gardener, with the assistance of the "foremost brain-anatomist of New York," is quite facetious over the assertion. Instead of head I should have said brain, and then the point involved would have been more correctly stated; for the scalp, muscles, fasciæ, etc., of the head have nothing to do with the issue which concerns the mind only as derived from the brain. In regard to the growth of the brain in size and weight, there is abundant authority for the statement that it ceases to advance at or about the seventh year. Soemmering states that the maximum is attained at three years. The brothers Wenzel, at between six and seven years; and Tiedemann, at between seven and eight years. Other observers have arrived at different results, but there is room for a difference of opinion on the subject, and Miss Gardener should have been aware of the fact when she dismissed the statement as though it were entirely unauthorized.
That the brain ceases to grow at a comparatively early age is abundantly established by the observations of several competent brain-anatomists. Thus, Dr. Boyd, who based his conclusions on the examination of over two thousand brains, found the average weight to be, at the age of from ten to twenty, 48·5 ounces the maximum weight for all ages, and four ounces heavier than in persons whose ages ranged from twenty to thirty.
Broca, quoting from Wagner's tables, gives the mean weight in persons of from ten to twenty years as 51·7 ounces heavier by 4·4 ounces than in persons from twenty to forty years of age.
The average weight of the brain in forty-seven persons of English, Scotch, and German nationality, as given by Thurnam in one of his tables, is 49·6 ounces in those whose ages range from ten to twenty years a weight considerably in excess of that shown for any other period of life.
The general truth of the assertion made in my paper on "Brain-Forcing in Childhood," that "the brain of a child is larger in proportion to its body than that of the adult" is, therefore, not only established, but the additional fact inferentially stated, that the brain is absolutely larger in childhood than in adults, is shown to be correct.
And now I must bring this communication to a close, feeling that I have given more attention to Miss Gardener than she and the "twenty leading brain-anatomists, microscopists, and physicians of New York" deserve, and advising them that before they again rush into print they make themselves to some extent acquainted with the elementary truths of the science of anthropology.
William A. Hammond.
THE EXPLOSION AT BRIGHTON, ILLINOIS.
Editor Popular Science Monthly:
Sir: The letter of Mr. A. O. Fay, published in No. 182, seems to call for a few words in reply, for Mr. Fay appears to have mistaken the purpose of the article to which he refers. In the first place, the entire aim of my article in No. 180 was to present the phenomena connected with the explosion of August 29, 1886, and not, as Mr. Fay seems
