The following is a very curious calculation of The Comparative Number of the Sexes at a Birth.

The celebrated M. Hufeland, of Berlin, has inserted in his Journal of Practical Medicine, some interesting observations in illustration of the comparative numbers of the sexes at a birth. The number of males born, to that of females, observes the learned Professor, seems to be 21 to 20 over the whole earth; and before they reach the age of puberty, the proportion of the sexes is reduced to perfect equality; more boys than girls die before they are fourteen. After extending his interesting comparison over animated nature in general, Professor Hufeland enters into an inquiry, peculiar to himself, in endeavouring to ascertain the principles and commencement of the equality of the sexes. In some families, says he, equality evidently does not hold. In some, the children are all boys; in others, all girls. He next proceeds to take several families, as 20, 30, 40, or 50, in one place, in conjunc tion; or small villages of 150 or 300 inhabitants. But even then, the just proportion was not yet established. In some years, only boys, in others only girls were born; nay, this disproportion continued for a series of a year or two; but by uniting ten or fifteen years together, the regular equality appeared. He next considered, that what took place in small populations must take place every year in larger societies; and he accordingly found it confirmed by actual enumeration. He went so far as, by the aid of the minister of state, Schack-man, to ascertain the comparative number of boys and girls bom in one day over the whole Prussian dominions, and the result corresponded with his anticipations. The general conclusions arrived at by M. Hufeland, are as follow:1st. There is an equal number of males and females born in the human race.- -2d. The equality occurs every day in a population of ten millions. - 3d. Every week in 100,000.- 4th. Every month in 50,000. - 5th. Every year in 10,000.- 6th. And in small societies of several families, every ten or fifteen years.-7th. That it does not occur in individual families.