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Rh It is to correct errors like this, which are wide-spread and do serious injustice to Mr. Spencer, that we have thought it necessary to go carefully into the subject, and furnish the evidence on which Mr. Spencer's claims to originality are founded.

was fitting that, at the Priestley centennial of the discovery of oxygen gas, two of the grandest achievements of modern science should have been called into requisition, to make the event known far beyond the circle of those who participated in the occasion. The telegraph reported the doings to all the contemporary world who cared about them, and the photograph preserved many of its interesting features pictorially, for the benefit of future generations. It was the general wish of those present that photographs should be made of the house which Dr. Priestley built and in which he died, and of the collections of his scientific apparatus. We are happy to see that this desire has been complied with, and a series of pictures taken, which represent the objects of chief interest in the celebration. No. I. is a group of chemists, representing 72 figures of the scientific men who attended the centennial meeting; No. II. Dr. Priestley's residence, showing the house and laboratory; No. III. Copy of a rare old engraving, showing the fury of the mob which destroyed Priestley's house in Birmingham; No. IV. Priestley's chemical apparatus; No. V. His electrical apparatus; No. VI. His physical apparatus. These three groups are from the Loan Exhibition. No. VII. Interior view of the Loan Exhibition; No. VIII. Head-stone of Priestley's grave. These photographs are mounted on eight by ten Bristol board, price 50 cents each, or $3.50 for. the set of eight. They may be ordered from Louis H. Laudy, School of Mines, Columbia College, New York.



did the country a service last year, by publishing his little volume entitled "Sex in Education," in which he called attention to some physiological points in the school-experience of girls, in such a way as to provoke half a score of replies, and to bring the subject very effectually before the public. He took ground against co-education, or the subjection of girls to the same conditions of study as boys, and showed how that system works serious and extensive injuries to the female constitution. The little volume now issued, while it is not a formal reply to his critics, pursues the subject of the physiological basis of education. Instead of dealing with mind as an abstraction, he takes up the brain in which it is embodied, and shows how mental development is, at bottom, really a process of "brain-building." Metaphysical vagueness is here escaped, and we have to deal with tangible and definite results that are dependent upon established laws. The body is thus brought into account, and we see how education, or mental development, is so deeply complicated with physiological conditions, that these can never be neglected in the intelligent consideration of mental culture.

At the close of this special essay, Dr. Clarke appends a mass of valuable testimony in regard to the practical workings of the system of co-education. The short article in our preceding pages, which we have entitled "Educated to Death," is taken from this portion of Dr. Clarke's book. By direction of the State Board of Health of Massachusetts, Dr. F. Winsor, of Winchester, collected some valuable statistics on "School Hygiene," and the effects of co-education formed one feature of the investigation. Circulars were sent to physicians, teachers, and others in the State, soliciting information in answer to questions. Replies were received from one hundred and sixty persons, of whom one hundred and fifteen are stated to be physicians; nineteen, physicians and members of school 