sects may be killed. The small flowering species seem to be preferred by the beetles, and are therefore recommended, as the goat's-beard (Spiræa aruncus), sorb-leaved (S. sorbifolia), and meadow spiræa (S. ulmaria). They are, moreover, desirable plants for their beauty. NOTES. PRIOR to the beginning of the eighteenth century opium was imported into China in comparatively small quantities, and mainly used as a remedy in dysentery. The vice of opium-smoking began in the latter half of the seventeenth century, but the drug was then too dear to permit the habit to spread rapidly; at the end of a hundred years, however, it had extended over the whole empire. The first edict against the practice was issued in 1796, and since then there have been innumerable prohibitory enactments, but all powerless to arrest the evil, which is now greater than ever before, and increasing in an alarming ratio. THE death is announced of Dr. Wilibald Artus, Professor of Philosophy at Jena, on February 7th last, aged seventy years. Also of Dr. Franz Xaver von Hlubek, Professor of Agriculture at the Graz Joanneum, on February 10th, aged seventy-eight years. In the third week of February also died Herr Adolf Müller, one of the directors of the well-known Geographical Institute of Justus Perthes at Gotha. CAREFUL investigation into the cause of the fire which broke out on the steamship Mosel revealed the fact that it originated spontaneously in silk goods which constituted a part of her cargo. Chemical examination showed that for every part of silk fiber "0-75 part of oxide of iron and 2:50 parts of coloring matter-consisting of fatty oils, organic and earthy matters-had been used to give weight and body to the silk." FROM data obtained by a series of elaborate experimental researches, Professor F. Rosetti estimates the effective temperature of the sun at 9,965° centigrade, taking into consideration the absorption produced by the terrestrial atmosphere. But, estimating also the absorption of the solar atmosphere, and calculating the thermal effect of the sun M. FAUTRAT has been convinced, by his if it had no atmosphere, the solar temperature would be 20,380 7° centigrade. studies of the influence of forests upon the moist currents that pass over them, that pines and other needle-leaved trees have a strong attraction for the vapor of water. He believes that the resinous trees transpire twice as much as other trees; and has also observed that when they are exposed to moist air they absorb vastly more water than the latter. THE deaths have been recently announced of two of the most prominent entomologists of Continental Europe. Ernest August Helmuth von Kiesenwetter was a member of the Saxon Privy Council, an accomplished and conscientious worker in the science, a considerable traveler, and a close observer. He was chiefly a coleopterist, but attended more or less to all orders of insects, while limiting his studies chiefly to those of Europe. S. C. Snellen van Vallenhoven, of Holland, was best known by his works on the insects of Holland, and his "Entomological Fauna of the East Indies." He also produced a work, which is still incomplete, on the "Ichneumonidæ of Northwestern Europe." All of his works were illustrated by beautiful and faithful drawings from his own pencil. MR. GRAMME is building for an establishment at Noisiel, France, a machine for transmitting electrical force to a distance, with which he expects to gain a normal power equivalent to that of ten horses, and under special conditions a power of sixteen horses. GENERAL WILLIAM MUNRO, of the British army, and a learned botanist eminent for his thorough and comprehensive knowledge of the grasses, died at his residence near Taunton, England, on the 29th of January, aged sixty-four years. THE French Government has taken action with a view to the protection of the domestic birds of the country, prohibiting in the several departments the pursuit of other than birds of passage, and those only under certain limitations. RECENT official reports show that the adulteration of food and drugs has largely decreased in Great Britain under the operation of the legislation against it. In 1856, when the "Lancet" commission made a report of its inquiries on the subject, more than half the samples analyzed were found to be adulterated. The first analysis under the act of 1875 was made in 1877, when it was shown that of the samples subjected to analysis the proportion of adulterated ones had fallen to 19.2 per cent. In 1878 the proportion fell to 17.2 per cent. If spirits be excluded from the calculation, the percentage of adulteration would be represented by 155 in 1877, from which it fell to 13.7 in 1878. THE French papers chronicle the death, at the age of eighty-two, of Dr. Boisdoval, a distinguished horticulturist, and author of a valuable work on the insects which affect garden-plants. THE POPULAR SCIENCE MONTHLY. JULY, 1880. THE INTERIOR OF THE EARTH.* By R. RADAU. HE additions that are being continually made to our knowledge of the composition and physical condition of the most distant heavenly bodies may well prompt one to ask why we are still so poorly informed concerning the constitution of the planet which the Creator has assigned to us for a dwelling-place. Mines and wells have barely scratched the solid crust that conceals the mysteries of the earth's depths. Our vague and uncertain ideas regarding the condition of the interior of the earth are based on analogies and inductions from facts observed on its surface or in the heavens. Very little light do we get on this subject from direct experiment. The bowels of the earth are not, indeed, easily accessible. Whatever the poet may say, the descensus Averni is not easily made; the domain of the stars is not thus hidden from us. For about two centuries large sums have been expended in the construction of gigantic telescopes with which to sound the depths of space; but no attempt, as a purely scientific undertaking, has been made to fathom the secrets of the underground world. The object of the numerous mines in different parts of the world has been simply the discovery of mineral riches, and the depths they have reached barely exceed, even in a few rare instances, a thousand metres; i. e., hardly the six-thousandth of the earth's radius— corresponding, on a globe thirteen metres † (about forty-two feet) in diameter, to a puncture one millimetre (about four one-hundredths of an inch) in depth. Notwithstanding this paucity of positive data, it will not be unin * Translated from the "Revue des Deux Mondes," by Guy B. Seely. VOL. XVII.-19 teresting to review the state of our knowledge on this obscure subject, and to show on what sides the question is accessible to science. The form of the planets is itself an index, to a certain point, of the mode of their origin and their actual condition. These slightly flattened globes that wheel about the sun have been subject to the same laws that shape the drop of water and the grain of shot. It is impossible not to believe that they are specimens on a vast scale of the equilibrated form assumed by free fluid masses through the action of internal forces which assemble and unite their molecules. All these spheroids have been or still are liquid drops that have become flattened by reason of their rotary motion. Newton was led to infer the flattening of the poles from the idea that the earth had originally been in a liquid state, as the centrifugal force due to rotation tends to swell the equatorial at the expense of the polar regions. By the operation of the same force that impels a stone when swung in a sling to free itself, and that causes grindstones to burst when turned too rapidly, the particles of a revolving sphere tend to fly from the axis of rotation, and this centrifugal force, nil at the poles, increases as the equator is approached, and there attains its maximum intensity. The effect of this is to diminish weight, substances being a little less heavy at the equator than at the poles. Imagine the earth completely liquid: the equatorial portion, driven by centrifugal force, will be elevated while the poles will be depressed. To better comprehend this, let us imagine a siphon, the two arms of which, joined at the center, issue, one at one of the poles and the other at the equator. The two liquid columns therein can remain in equilibrium, as the globe revolves, only on condition that the equatorial column, which is exposed to the action of centrifugal force, be longer than the polar column, which has lost nothing of its weight from this cause. The sphere becomes a flattened spheroid. This change of form can be demonstrated by turning rapidly on its vertical axis a sphere of clay or of flexible steel circles, as used in illustration of physics. As the pliant mass solidifies more or less completely, this flattened form is preserved. That there is a discrepancy between weight at the equator and at the poles, more marked as we approach or recede from one or the other, may be shown by noting, by the tension of a spring, the weight of the same mass under different latitudes; but a more positive means of ascertaining this fact is furnished by the oscillations of the pendulum, which are retarded as the force of the earth's attraction diminishes. The astronomer Richer, having been sent to Cayenne in 1672 to observe the planet Mars, remarked that a timepiece regulated at Paris lost ten and a half minutes daily at Cayenne. It was this circumstance, at first inexplicable, that led Newton to suspect that the earth was a flattened spheroid. It will be evident that an exact knowledge of the figure of the earth |