28 TEE POPULAR SCIENCE MONTELY. 



orbits of the planets, whose evolution requires some finer if more com- 

 plex fore-ordination than merely the existence of two masses undis- 

 turbed by any other matter in space. 



I shall only say in conclusion : Assuming the sun's mass to be com- 

 posed of portions which were far asunder before it was hot, the imme- 

 diate antecedent to its incandescence must have been either two bodies 

 with details differing only in proportion and densities from the cases we 

 have been now considering as examples ; or it must have been some 

 number more than two some finite number at the most the number 

 of atoms in the sun's present mass, which is a finite number as easily 

 understood and imagined as number 3 or number 123. The imme- 

 diate antecedent to incandescence may have been the whole constitu- 

 ents in the extreme condition of subdivision that is to say, in the 

 condition of separate atoms ; or it may have been any smaller number 

 of groups of atoms making up minute crystals or groups of crystals 

 snow-flakes of matter, as it were ; or it may have been lumps of matter 

 like this macadamizing stone ; or like this stone, which you might 

 mistake for a macadamizing stone, and which was actually traveling 

 through space till it fell on the earth at Possil, in the neighborhood of 

 Glasgow, on April 5, 1804 ; or like this which was found in the Desert 

 of Atacama in South America, and is believed to have fallen there from 

 the sky a fragment made up of iron and stone, which looks as if it 

 had solidified from a mixture of gravel and melted iron in a place 

 where tliere was very little of heaviness ; or this splendidly crystal- 

 lized piece of iron, a slab cut out of the celebrated aerolite of Lenarto, 

 in Hungary;* or this wonderfully shaped specimen, a model of the 

 Middlesburgh meteorite, kindly given me by Professor A. S. Her- 

 schel, with corrugations showing how its melted matter has been 

 scoured off from the front part of its surface in its final rush through 

 the earth's atmosphere when it was seen to fall on March 14, 1881, 

 at 3.35 p. m. 



For the theory of the sun it is indifferent which of these varieties 

 of configurations of matter may have been the immediate antecedent 

 of his incandescence, but I can never think of these material ante- 

 cedents without remembering a question put to me thirty years ago 

 by the late Bishop Ewing, Bishop of Argyll and the Isles : " Do you 

 imagine that piece of matter to have been as it is from the beginning ; 

 to have been created as it is, or to have been as it is through all time 

 till it fell on the earth ? " I had told him that I believed the sun to be 

 built up of stones, but he would not be satisfied till he knew, or could 

 imagine, what kind of stones. I could not but agree with him in feel- 

 ing it impossible to imagine that any one of these meteorites before 

 you has been as it is through all time, or that the materials of the sun 

 were like this for all time before they came together and became hot. 



* The three aerolites now exhibited belong to the Ilunterian Museum of the University 

 of Glasgow, and have been kindly lent me for this evening by the curator, Dr. Young. 



