DESCRIPTION OF A NEW AND IMPROVED DISSOLVER FOR THE MAGIC LAN TERN WITH EXHIBITION OF SLIDES. By Dr. E. P. HOWLAND, Washington, D. C. [ABSTRACT.] As the magic lantern has got to be the most important philosophical instrument for scientific and popular illustrations, any improvement in its constructions or arrangement for its manipulation is of scientific and public interest. A complete dissolver for the lantern is one in which the quantity of the gases for each lantern used is regulated by separate needle valves and independent of the dissolving cock. There should be no diminution or increase of light in any lantern caused by increasing or diminishing the supply of gases to or from another lantern. It should be so constructed that all the lanterns used could be in full light at the same time or any one or more of them extinguished or relighted without affecting the light of the other lanterns. Most of the dis solvers on the market are constructed for using with two lanterns only, and take the gases from the first lantern to illuminate the second, thereby diminishing the light from the first picture before the second gets fully illuminated, making a dark point between the change of the pictures. The advantages of a good dissolver, besides not having the picture darken down in dissolving, is so that we can have as many pictures on the screen at the same time as we have lanterns and have them all equally illuminated. We then can have different illustrations on the screen side by side, or a picture with figures dissolved in, or a background of different or changing colors with many beautiful aud artistic arrangements. A great variety of beautiful and interesting lantern slides were shown with two, three and four lanterns dissolving. SPECTRO-PHOTOMETRIC COMPARISON OF SOURCES OF ARTIFICIAL ILLUMINATION. By Dr. E. L. NICHOLS, Cornell University, Ithaca, N. Y., and W. S. FRANKLIN, University of Kansas, Lawrence, Kan. ON THE RADIATION OF HEAT BETWEEN METALS BY INDUCTION AND BY CONDUCTION, WITH NUMERICAL RESULTS FOR STEEL AND BRASS. By Prof. WM. A. ROGERS, Colby University, Waterville, Me. ON THE DEFINITIONS OF THE TERMS WEIGHT AND MASS. By Prof. Wм. A. ROGERS, Colby University, Waterville, Me. THE CAUSES OF SUDDEN VARIATIONS OF ATMOSPHERIC PRESSURE. By DESCRIPTION OF APPARATUS FOR MAKING A LIGHT-WAVE THE STANDARD OF LENGTH. By Prof. A. A. MICHELSON, U. S. N., and Prof. EDWARD W. MORLEY, Cleveland, Ohio. TWO STROKES OF LIGHTNING. By Prof. J. W. MOORE, Lafayette College, Easton, Penn. A GALVANOMETER FOR THE VERTICAL LANTERN. By Prof. J. W. MOORE, Lafayette College, Easton, Penn. OFFICERS OF SECTION C. Vice President. C. E. MUNROE of Newport, R. I. Secretary. WILLIAM L. DUDLEY of Nashville, Tenn. Member of Council. EDWARD HART of Easton, Pa. Members of Sectional Committee. R. B. WARDER of Washington, E. W. MORLEY of Cleveland, Ohio, Member of Nominating Committee. A. P. S. STUART of Lincoln, Neb. Members of Sub-committee on Nominations. E. H. KEISER of Bryn Mawr, Pa., O. C. JOHNSON of Ann Arbor, Mich., 2 |