<>1() SCIENTIFIC RECORD FOR 1885. 



ill defiued, uuited together and nebulous. But in a few seconds after 

 starting- it the lines became clear and remarkably sharp, continuing so 

 as long as the motion continued. But now the effect of temperature be- 

 came apparent in the shifting of the lines toward the red if the prism 

 was rising and toward the blue if falling in temperature. For a change 

 of about 9° the shifting was something over 3*5 inches. To overcome 

 this shifting the prism was inclosed in an even-temperature box, and 

 by means of a simple but ingenious thermostat the temperature was 

 regulated so that in seven hours it varied by an amount suificient to 

 shift the sodium lines by only the distance between them. {Am. J. 

 Sci., April, 1885, III, xxix, 209.) 



Langley has investigated the optical properties of rock salt worked 

 into prisms by Clark and by Brashear with such exquisite surfaces 

 that they give a spectrum showing the Frauuhofer lines with all the 

 sharpness of Hint glass. Indeed, a rock-salt prism made by the latter 

 shows the nickel line between the Ds. Experiments with a train of such 

 prisms were made to determine not only the indices for different lines 

 in the visible and invisible spectrum, but also the apparent transmis- 

 sion of rock-salt plates for different parts of the spectrum. Heat spec- 

 tra were formed from radiating sources below the temperature of melt- 

 ing ice, and it was found that most of the rays, even from these sources, 

 passed freely through the prism. With the smallest deviations, corre- 

 sponiliug to wave lengths exceeding probably 109,000 of Angstrom's 

 scale, a slight absorption began to be noticed. A table is given of the 

 refractive indices of a prism of angle 59° 57' 54" for the spectrum lines 

 from M in the ultra violet to il in the ultra red ; or from wave length 

 0'3727 to 1-32. The values in the visible spectrum are given to six 

 places, those in the ultra red to four. For the line M, the refractive 

 index is 1-57480; for G, 1-50133; for D, 1-54418; for A, 1-53070; and 

 for .(}, 1-5208. In all, seventeen indices were measured. {Ain. J. Sci., 

 December, 1885, III, xxx, 477.) 



Lommel has suggested the use of phosphorescent substances, such 

 as Balmain's luminous paint or a greenish-blue variety of phosphores- 

 cent calcium sulphide, for the purpose of rendering visible the focus of 

 ultra-red rays in the well-known experiment of Tyndall on calorescence. 

 If such a powder be made slightly iihosphorescent by exposure to or- 

 dinary daylight the less refrangible rays increase it to a bright lumi- 

 nosity. In place of a solution of iodine in carbon disulphide as the 

 absorbing solution, Lommel recommends a solution of nigrosiu in alco- 

 hol or chloroform, preferably the latter. {Wied. Ann., 1885, xxvi, 157; 

 Phil. Mag., December, 1885, Y, xx, 547.) 



Lommel has shown that if a conical beam of solar light be allowed 

 to fall on a cube of Iceland spar, either directly or after passing a co- 

 balt-blue glass, the cube emits a beautiful brick red light. This light 

 is not polarized and its composition does not depend upon the state of 

 polarization of the incident beam. It is comprised between 35 and 05 



