IX. MISCELLANEOUS. 249 



appear very brilliant ; as soon, however, as the white reflecting sheet is 

 removed, and the globules rest on a dark dull ground, the brilliancy at once 

 disappears. 



The preceding experiment can also be well executed with solidified drops of 

 Canada balm. 



97 5a. Apparatus of M. Sravais, for producing halos, 

 parhelia, and other kindred phenomena. W. G. Lettsom. 



It consists of a hollow equilateral prism made with plates of parallel glass. 

 The prism is filled with water at an orifice on the top. It is fixed on a 

 vertical axis rotating by clockwork. With 100 revolutions in a second it 

 reproduces the varied series of positions of the vertical prisms of ice producing 

 parhelia. The prism is to be illuminated by a beam of sunlight, or by a lamp 

 at a distance of 8 or 10 yeards. The apparatus reproduces also the Anthelion ; 

 by substituting for the prism a quadrangular plate of glass turning round on 

 one of its vertical edges. If striae are traced on the surfaces of this plate, 

 the anthelion becomes traversed by two symmetrical arcs, arranged in the 

 form of a St. Andrew's cross. 



See M. Bravais's Memoir e sur les Halos, Paris, 1847, p. 266, 4to. ; or 



Journal de I'EcoIe Royale Poly technique, XXXI. cahier. 



976^ Four Absorption Cases, all in glass, 5 and 10 mm., 

 and two pieces for spirits and water. 



Warmbrunn, Quilitz, and Co., Berlin. 



977. Bunsen's Apparatus for Experiments in Spectrum 

 Analysis, a battery of four Ley den jars, a stand with arrange- 

 ments for producing a spark spectrum, with holder for spectrum 

 tubes. Reiser and Schmidt, Berlin. 



978a. Apparatus for measuring the magnitude of Gas 

 Jets at a distance. Invented by Mr. C. Wolfberger. 



Geneva Association for the Construction of Scientific In- 

 struments. 



This apparatus, invented by the civil engineer Wolfberger, is intended for 

 the comparison of gas lamps from the street level. 



Founded on the principle of the sextant, it is composed of two mirrors : 

 the one fixed, the other movable parallel to the first along a graduated scale. 



In order to measure the magnitude of the gas jet, the operator holding 

 the instrument by its handle on a level with the visual ray, and looking 

 through the sight, observes simultaneously, in a direct line, the jet to be 

 measured, above the fixed mirror, and indirectly the image of the same jet by 

 double reflection. The screw-head placed below the handle is then turned, 

 until the right edge of the jet, seen in a direct line, coincides with the left 

 edge of the jet, seen by reflection. The magnitude of the flame, ascertained, 

 is then shown on the metallic scale which is read in millimetres. 



978b. Patent Illuminating Power Meter, for showing the 

 illuminating power of gases in the terms of the Parliamentary 

 sperm candles and the standard quantity of five cubic feet of gas 

 per hour by the observation of one minute. William Sugg. 



