POGGENDORFF's Annalen der Physik und Chemie, vol. cxl., part 2.—This number of Poggendorff's Annalen contains (1) the conclusion of Ketteler's paper on the theory of Chromatic Dispersion. (2.) The conclusion of Sondhaus's paper on the “tones of heated tubes, and on the vibrations of air in organ-pipes of various shapes.” In this part the author compares his formula with Wertheim's experimental results, and shows that in most cases the agreement between them is very close. (3.) The conclusion of Freese's paper on chromates. (4.) “On the work done by gases in motion,“by L. Boltzmann. In the first volume of the Annalen for 1869 (vol. cxxxvi.), a method of determining the specific heat of air under constant volume is described by F. Kohlrausch, the method consisting essentially in observing the cooling effect indicated by a delicate metallic thermometer enclosed in the receiver of an air-pump when the piston is raised. A few months afterwards (Pogg. Annalen, vol. cxxxviii.) Kohlrausch's experiments were criticised by A. Kurz, who objected to them that when the air in the receiver of a pump is expanded by drawing up the piston, it does no work; and that, therefore, theoretically, its temperature ought not to fall. This is of course an obvious blunder; and Boltzmann shows, by a strict mathematical discussion of the experiment, that although the pressure of the air against the piston, and therefore the work done by it, is not quite so great when the piston is raised quickly, as it would be if the movement were indefinitely slow, yet the difference is only a quantity of the same order as the ratio of the velocity of the piston to the velocity of sound, and therefore cannot have perceptibly affected Kohlrausch's results. (5.) “Calculation of the vibrations of a string, taking account ot its rigidity,” by R. Hoppe. (6.) “On asterism and corrosion figures in crystals,” by H. Baumhauer. (7.) "Comparison of the electrophorus with the electrical machine and the electro-phorus-machine,” by P. Riess. This paper contains some interesting historical notices of early electrical machines, bolh fric-tional and such as acted by induction, but we cannot see that it is of any importance as a contribution to the theory of electrical machines. (8.) “On the velocity of molecular motion and that of sound in gases,” by E. Mulder. The author seeks to establish a relation between the velocity of sound in a gas and the mean velocity of translation of its molecules, as deduced by Clausius from the dynamical theory of heat. (9.) “On the production ot stationary vibrations and sound-figures in liquidsand gases by solid sounding plates,” by A. Kundt. (10.) “On elastic vibrations, ” by J. J. Miiller. By a modification of Kundt's method of measuring the wave-lengths of vibrating columns of air, the author has succeeded in proving that the velocity of propagation of vibrations of great amplitude is perceptibly greater than that of vibrations of small amplitude, both in the case of columns of air and of elastic rods. (11.) “On Leclanchés Manganese battery,” by J. Müller. The author finds that polarisation occurs to a considerable extent in galvanic cells of Leclanchés construction when they are employed in a circuit of small resistance, so that under these circumstances he found the electro-motive force of a Leclanchés cell to be only O.896 of that of a Daniell's cell, whereas, according to Leclanché, it is equal to 1.38 times the electro-motive force of a Daniell's cell. (12.) “On the occurrence of augite-material in meteorites,” by C. Rammelsberg. (13.) “On the Lodran meteorite,” by G. Tschermak. (14.) “On acoustic attraction and repulsion,” by K. H. Schellbach. Additional facts, but as yet no explanation of these curious phenomena. According to the author, the attraction of light bodies by a vibrating tuning-fork was observed and described by Guyot in 1834. (15.) “On the maximum-density and freezing point of mixtures of alcohol and water,” by F. Rossetti. This is a short extract from the author's researches on the expansion of water and certain solutions, published in greater detail in the Annates de Chimie et de Physique for 1867 and 1869 (vols. x. and xv.). (16.) “A Method of Examining the Structure of Flames,” by L. Dufour. The flame is cut across horizontally by a flat lamellar jet of water or of air, and can then be examined at leisure by looking down into it from above. (17.) “Remarks on the colour of iodine,” by Carl Schultz-Sellack. The author calls attention to the different colour of iodine in the solid state, or when dissolved in water, alcohol, &c., from that which it shows in the state of vapour, or when dissolved in sulphide of carbon, stannic chloride &c., iodine transmitting in the former case chiefly the extreme red rays of the visible spectrum, and, in the latter case, chiefly the blue and violet rays. He argues that this difference of absorptive character between solid or liquid and gaseous iodine is analogous to the difference which exists, according to Magnus, between the absorptive action of liquid and gaseous water on invisible heat-rays. (18.) Prof. Nordenskiöld announces the discovery of platinum as well as gold in the sand of the river Ivalo in North Lapland. (19.) The genuine character of the diamond lately found in Bohemia has been proved by Prof Schafarik by burning a portion of it in oxygen.