merely momentary exposure was sufficient to destroy the reaction of such a tache. 2. A similar Soda tache, treated in like manner, required a somewhat longer time for its dissipation. 3. Tache of Carbonate of Potassa, having a very strong reaction. a. Heated over lamp for 10"; reaction much reduced. b. 99 99 tache dissipated. for 15"; reaction entirely destroyed, and c. Ignited intensely, for a moment, by blowpipe: reaction destroyed whenever the ignition was complete. d. Ignited intensely for 2"; reaction in every case destroyed. 4. Tache of Carbonate of Soda, having a very strong reaction. a. Heated over lamp for 10"; reaction reduced to about . 5. Tache of Magnesia. This was formed by evaporation of a solution of carbonate of magnesia in carbonic acid water. Until ignited, therefore, the tache consisted of carbonate of magnesia. a. The simple tache gave strong alkaline reaction. b. Ignited gently over lamp for a moment; reaction slightly increased. c. Ignited gently for 10"; reaction reduced to two-thirds. d. Ignited intensely by blowpipe for 10"; reaction about 1-20th of (a). e. Ignited intensely for 30"; reaction about 1-50th of (a), but still very distinct. 6. Tache of Lime. Formed as the preceding, in the first instance a carbonate. a. The reaction of the simple tache extremely faint, scarcely perceptible. b. Ignited over lamp for a moment; reaction very intense. d. Ignited, as above, for 30"; very slightly diminished. 1. Carb. Potassa. II. Experiments by Weighing. 1 grain of pure, thoroughly dried carb. potassa, in platina capsule, exposed to intense ignition, over table blowpipe, lost in 1', 0.2 grains. In a little less than 10', it was entirely dissipated. 2. Carb. Soda. 1 grain of pure, perfectly dry carb. soda, ignited intensely over the table blowpipe for 10', lost 0.35 grains. 3. Magnesia. 1 grain, similarly treated, lost in 1', only 1-100th grains. In 10', its loss was 8-100 grains. 4. Lime. 1 grain of lime, similarly exposed, for 10', exhibited no sensible loss. Reference was made to the bearings of this determination upon chemical analysis. First, as furnishing the means of recognising the presence of the alkalies and the alkaline earths in mineral substances, such as the felspars, hornblends, epidote, &c.; and, secondly, as indicating the probable large loss of the alkalies of vegetable matters, through the intense heat used in converting them into ashes. Allusion was made also to the almost entire absence of the alkalies in the ashes of anthracite and other coals, as dependent upon the intense heat operating in their combustion; and experiments were adduced, to show that the coal, prior to the combustion, contained alkaline matter in a marked quantity. The volatility of magnesia, as compared with lime, was spoken of as useful in distinguishing between magnesian and calcareous minerals. The application of this property of magnesia to the theory Dolomization was also briefly referred to. Prof. W. B. ROGERS moved that a Standing Committee be appointed for this Section, to arrange the order of business for each day; which was adopted, and the following gentlemen appointed: Prof. W. B. ROGERS, Chairman; Profs. B. PEIRCE, B. SILLIMAN, JR., J. H. C. COFFIN and J. H. COFFIN. The Section then adjourned till 4, P. M. Afternoon Session. On the reassembling of the Section, Prof. B. PEIRCE read a paper UPON CERTAIN METHODS OF DETERMINING THE NUMBER OF REAL ROOTS OF EQUATIONS, APPLICABLE TO TRANSCENDENTAL AS WELL AS TO ALGEBRAIC EQUATIONS. Sturm's theorem is perfect for algebraic equations, but is generally too cumbrous for practical use. By stopping, however, at the first, second, or third of his functions, whenever either of these is sufficiently simple for direct discussion, the number and nature of the real roots of the given equation can be readily ascertained. Prof. Peirce illustrated this method by geometrical diagrams, and applied it to some very general cases of algebraic equations. This was followed by an article ON THE ALLEGED INSOLUBILITY OF COPPER IN HYDROCHLORIC ACID; WITH AN EXAMINATION OF FUCH'S METHOD FOR ANALYZING IRON Ores, MetallIC IRON, &C. BY PROFS. R. E. and J. B. ROGERS. Prof. R. E. ROGERS, in presenting this communication, referred to the received opinion among chemists, that metallic copper is almost entirely insoluble in pure hydrochloric acid, when oxygen is absent; this, which has been made the foundation of an analytical process, first recommended by Fuch, and since by Fresenuis, was found to be inaccurate. By a particular apparatus, in which carbonic acid gas, in one case, and hydrogen gas, in another, was made to flow into the space above the liquid and metal, so as effectually to exclude the atmosphere, it was found that continued boiling caused the copper to be dissolved in marked quantity. Even when exposed to the acid at ordinary temperatures, the atmosphere entirely excluded, it was found that, after a prolonged time, the metal underwent partial solution, bubbles of hydrogen were evolved, and the dichloride of copper was formed. The Professors R. regard these results as clearly proving the incompetency of Fuch's method to afford accurate results. The following paper was then read: ON SOME PHYSICAL PHENOMENA DEPENDENT UPON THE PROGRESSIVE MOTION OF LIGHT. BY PROF. STEPHEN ALEXANDER. After adverting to the recognised effect of the annual aberration of light, and that which is ordinarily termed planetary aberration, the author more particularly explained the dragging of the shadows of the earth and other planets, first previously noticed by himself in a communication to the American Philosophical Society. Prof. A. then proceeded to the consideration of the case in which light passed through the transparent envelope of a body in motion, and observed that inasmuch as the theory of undulation required that the ether should be possessed of inertia, and the inertia of our atmosphere must be incomparably greater than that of the ether, it would seem to follow that the velocity of the earth's atmosphere, due to its annual motion, must be impressed upon the light of the sun and stars in the passage of the same through the atmosphere, and thus produce an aberration which, in so far as the earth's motion was concerned, would be the opposite to that which actually exists. As to aberration being, both in mode and measure, what it ought to be, if the earth had no atmosphere, Prof. A. suggested that the explanation of this was to be found in the enormous porosity of the atmosphere; by far the greater portion of the rays, so passing through as to escape the mechanical action of the molecules. When, however, the quantity of atmosphere to be traversed was so great that light must be nearly absorbed, some sensible portion of it might be subject to the influence in question. Prof. A. then referred to the phenomenon of a blue band, seen by himself and others, bordering that edge of the earth's shadow into which the moon entered at the time of the last lunar eclipse, but which was less distinct on the side at which the moon emerged; and showed that these phenomena were consistent with the supposition of such an impulse, accompanied by the dragging of the shadow. Lastly, Prof. A. suggested that these considerations might have a bearing upon the question of a systematic aberration of the double stars; for if the nature of the envelope of a star were such that its mechanical impulse could be communicated to the light of the star, the theory of emission, with reference to such a star, would be quasi true, and the aberration admissible. The Section then adjourned to meet at 10, A. M., to-morrow. September 22. SECTION OF NATURAL HISTORY, GEOLOGY, &c. Second Meeting. The Section met and was organized-Dr. SAMUEL GEO. MORTON in the chair. A paper was read: - ON THE FORCES IN NATURE WHICH RUPTURE, CONTORT, UPHEAVE, AND DEPRESS THE SUPERFICIAL STRATA OF THE EARTH. BY PROF. L. J. GERMAIN. Mr. G. remarked, that it was familiar to every one, that the planes of the terrestrial equator and the plane of the ecliptic, form an angle of about 23° 28'. There are two motions of the earth, aside from its perturbations, namely, its diurnal revolution around its own axis, and its annual revolution around the sun-each of which revolutions tends to flatten the earth in the direction of their resultant force, in a plane whose direction is intermediate between the direction of the two, operating on the crust of the earth most effectively within the limits of the torrid zone. It was this resultant centrifugal force to which Mr. G. called particular attention, as the substance of his theory of flattening, upheavals, and depressions. Prof. AGASSIZ favoured the Section with his Observations ON THE PHONETIC APPARATUS OF THE Cricket. The Professor gave an account of the structure of the Phonetic Apparatus of insects of the order Orthoptera, particularly the crickets. He observed that he had been led to these investigations by some interesting remarks upon the wings of the grasshopper, in the Transactions of the Academy of Natural Sciences of this city. The wings of the grasshopper have elastic springs, by which they are folded, when in a state of repose. Prof. A. proceeded to demonstrate the structure of these wings on the black-board. It had occurred to him that the same structure might be found in other insects also, and upon investigation, he had discovered this to be the case. The same general formation is common to all insects of the order of Orthoptera, and is a distinguishing feature of all the varieties of that large and interesting group. It is (remarked Prof. A.) by the action and contact of these springs, that these insects produce their music. Prof. HALDEMAN exhibited a series of specimens of Phacops Hausmanii. (Calymene Micrurus. Green). The head and tail of this species are the only portions hitherto discovered; but one of the specimens, now presented, contains the body which has eleven segments. Prof. HALL added some remarks on the same subject. Prof. AGASSIZ now gave his views— ON THE COMPARISON OF ALPINE AND NORTHERN VEGETATION. His remarks referred principally to the general observations of Humboldt; but many facts observed on the North American continent F |