Page:Popular Science Monthly Volume 1.djvu/785

Rh trees were of the female kind. He specifies that the larch, while in its highest luxuriance, and during many years, produces only female flowers; but in its decline it at length produces male flowers, and it shortly afterward dies. Prof. Hartshorne extended this theory to animal life, and undertook to show that, whenever or wherever there was excess of formative power, its tendency was to the production of female offspring. He illustrated his belief by the development of bees, the birth of the queen-bee being the highest, of the drone the lowest result, and preceded by respectively high and low circumstances of nutrition. Sometimes a working-bee—which, being an imperfect female, is of course incapable of impregnation—will give birth to parthenogenetic offspring. Such offspring is always male. The eggs of the queen-bee that hatch males have not been fertilized; and, should she never have been impregnated and lay eggs, they will hatch only drones. In respect to the aphides (plant lice), it is noticeable that, while their food is sufficient and of nutritious quality, their offspring is exclusively females, propagated parthenogenetically; but soon after the supply of food, owing to a change of season or circumstances, is diminished, young male aphides appear. Among the higher order of animals Prof. Hartshorne found an argument in the sex of double monsters. Stating that the birth of double monsters was due to fissure of the ovum and excess of formative power, he asserted that it is well known that in the majority of instances these monsters were of the female sex. He brought forward the vital statistics of different nations and their varying proportion of male and female births in support of his position, attributing the differences to increasing or diminishing vitality; and even the continually lessening reproductive powers of American women formed one of the illustrations of this theory.

Prof. Joseph Lovering, of Cambridge, Mass., gave an interesting address on vibration, illustrated by an experiment. It was presumed that the members were more or less familiar with Milde's experiment with a tuning-fork and vibrating thread. This optical method of Milde is very much improved by using a large bar of iron and perpetuating the motion by means of magnetic excitement, the vibration being thus maintained for any length of time. A cord 20 or 30 feet in length is thus thrown into vibration. When the first suspension bridge was building in England, a fiddler offered to fiddle it away. Striking one note after another, he eventually hit its vibrating note, or fundamental tone, and threw it into such extraordinary vibrations that the bridge-builders had to beg him to desist. Only recently a bridge went down under the tread of infantry in France who had not broken step, and 300 were drowned. An experiment is often referred to of a tumbler or a small glass vessel being broken by the frequent repetition of some particular note by the human voice. It is said, and may be true, that certain German tavern keepers increase their custom by the occasional performance of this feat. In the Talmud there is a curious question raised as to what would be the damages if a domestic vessel were broken by a noise made by an animal, such as a barking dog. Prof. Lovering here exhibited two pieces of clock-work, each giving a button a circular velocity of rotation. These are to turn a cord much as a skipping-rope is turned. The rotation twists an ordinary cord—or untwists it, as the case may be—and to avoid this twisting a tape is substituted, and a twisting or rotating machine is placed at each end. The chief difficulty now remaining is to have the machines twist in unison, which is difficult, as the two pieces of clock-work vary from each other, but on the whole the experiment is usually satisfactory. The tape was stretched across the stage, and the machines to rotate it were placed at each end. If the string is too slack for one segment of vibration, it subsides into parts, each having a vibration similar to the other. The tighter the string is drawn, the fewer the segments of harmonic vibration. The string started with five waves or segments of vibration. Drawn tighter, these were reduced to four, three, and finally two segments, the nodal point in each instance between the waves remaining perfectly unmoved. With a shorter string the first harmonic note was reached, and