Notes and Memoranda. 159 



whether or not light is to he regarded as the vibrations of an imponderable 

 material. 



Constitution of Stjn and Stars. — Mr. GL J. Stoney has a remarkable paper 

 in " Proc. Koy. Soc.," No. 94, disclosing speculations on this subject, to which 

 he assigns varying degrees of probability. He remarks, that if, as is probable, the 

 sun's atmosphere decreases in temperature from within outwards, the gases with 

 the lightest particles will be uppermost, and the heavier ones lower, and these 

 layers of gases will be of different temperatures, hydrogen being the coldest. 

 Observation, he thinks, confirms this view, " the rays of hydrogen, sodium, and 

 magnesium emanate from a region so cold, that the lines of these elements in the 

 sun's speculum are intensely black ;" while " calcium, iron, and the rest, whiie 

 they produce only black lines in the violet and indigo, give rise to lines which are 

 sensibly less dark in the blue, and to lines which emit a still more considerable 

 light in the green, yellow, orange, and red — those colours in which a body gra- 

 dually heated begins to glow. Hydrogen and iron are the two most abundant 

 constituents of the sun's outer atmosphere, and play in it the same part which 

 nitrogen and oxygen do in the earth's." The photosphere consists of two strata, 

 the outer one of cloud, that is solid or liquid matter in minute division, and 

 denser than the atmosphere in which it is dispersed. Cooling by radiation, these 

 clouds rain down their materials as our water clouds do theirs. This cooling he 

 believes to give rise to a layer of minimum cloud temperature, the strata above 

 and below being hotter. " About the middle of the hot stratum over the pho- 

 tosphere, outside which the temperature decreases almost continuously to the 

 limit of the iron atmosphere." Outside this, in another stratum, he thinks the 

 temperature falls short of the heat of a Bunsen burner ; and outside this again, 

 " through the immense height which is tenanted by sodium, magnesium, and hydro- 

 gen alone, the temperature goes on decreasing, till it becomes excessively cold." 

 " Within the luminous clouds the temperature very rapidly waxes, and the 

 density too appears to receive a nearly sudden increase, all gases with a vapour- 

 density more than about eighty times that of hydrogen are imprisoned within the 

 shell of clouds by the comparative chill which there prevails co-operating with the 

 force of gravity exerted by the sun." Applying these theories to the stars, Mr. 

 Stoney observes, that " when gravity on a star is feebler than on the sun, either 

 from the mass of the star being less, or from its being so dilated by heat that its 

 outer parts are farther removed from its centre gases, which by reason of the 

 mass of their molecules are imprisoned within the photosphere of the sun, will, 

 when less- attracted downwards, be able to stand the coolness of the shell of 

 clouds, and pass beyond them. Thus mercury, antimony, lithium, and bismuth, 

 all of which have too high a vapour density to exist in the sun's outer atmo- 

 sphere, show themselves in Aldebaran." Stars in which the temperature is 

 lower, or gravitation acts with more force, will attract down dense materials from 

 their outer atmosphere, and constitute the class of intensely white stars with a 

 bluish tinge like a Lyra and Sirius. Hydrogen has so low a molecular mass, that it 

 is thought no star exerts attractive force enough to compel it to limit to temperatures 

 which would make it appear bright when placed upon the background of their 

 photospheres, and hence, where hydrogen appears at all, it3 spectrum lines are 

 intensely black. To account for the colours of double stars, he supposes that 

 collisions of stars take place, and that the two stars thus meeting, emerge from 

 the frightful conflagration that ensues as one star, or as two, having orbits that 

 would lead to fresh collisions, or passage through each other's atmosphere, in 

 the course of which the weaker, or companion star, would be deprived of its 

 lighter gases, and thus emit only the colours proceeding from denser gases, blue, 

 violet, and green. 



The 92nd Planet. — On the 26th July, Dr. Peters, of Hamilton College 

 Observatory, Clinton, U.S., discovered this body, which is of the 11th mag. It 

 has been named Undina. 



Eoman Sueoicai Instruments. — M. H. Scoutetten describes to the French 

 Academy a collection of surgical instruments found at Herculaneum and Pom- 

 peii. He says three hundred specimens have been collected, representing sixty 

 different forms of instrument. Amongst others, he mentions sounds of excellent 

 curves, and specula with two and three valves. Having obtained permission of 



