92 Transactions of the 



liquid nucleus, heated to a temperature of the brightest whiteness, 

 which is surrounded by an atmosjjhere of somewhat lower temper- 

 ature. Within the last two or three years we have obtained some 

 knowledge about the mysterious red protuberances which are seen 

 on the circumference of the sun at the time of an eclipse. From 

 experiments made with the spectroscope, they appear to consist of 

 hydrogen in a state of ignition. It is supposed that they some- 

 times reach the height of 80,000 or 90,000 miles. 



Let us now glance at the properties of the light from the fixed 

 stars. By proper instruments, physicists have been enabled to 

 learn as much about the atmosphere and the physical constitution 

 of the stars, as about the composition of the solar atmosphere. 

 But still it has been acquired by much toil and labour. As the 

 light emitted by the stars is very feeble, most delicate instruments 

 are required, which have to be constructed with the greatest care 

 and expense. The spectra of several stars have been examined. 

 In Aldebaran two hydrogen lines, C and F, are present, but in 

 a Orionis these are alisent, therefore it is concluded that hydro- 

 gen is present in Aldebaran, but absent in a Orionis. In the 

 same way it is seen that silver is not present in Aldebaran, nor in 

 a Orionis, but that four bright lines of calcium, also seen in the 

 sun's spectrum, are present in both stars. In Aldebaran no less 

 than nine elements have been detected, namely : — 



1. Hydrogen. 4. Calcium. 7. Tellurium. 



2. Sodium. 5. Iron. 8. Antimony. 



3. Magnesium. 6. Bismuth. 9. Mercury. 



We see that four elements are thus found in Aldebaran wliich do 

 not exist in the sun. All the stars observed contain hydrogen, 

 except Betelgeux and /3 Pegasi. DiflFerent coloured stars give 

 spectra in which there is a greater absence of dark lines in the 

 rays which are of the same colour as the stars than in the other 

 parts. It is interesting to know that the spectra of fixed stars 

 contain, like the solar light, invisible chemically active rays. Mr 

 Huggins has photographed the spectrum of Sirius. The intensity 

 of the light of this star has been calculated to be about the s. ooo.ooo.ouo 

 of that of the sun ; and although probably not less in size than 

 sixty of our suns, the distance of it from our earth is estimated 

 to be more than 130,000,000,000,000 miles ! And yet, at this 

 great distance, we can register the chemical intensity of the rays 

 which left Sirius twenty-one years ago. Mr Huggins has also 

 examined those mysterious bodies the nebulae, and has found that, 

 instead of having bands of liglit intersected by dark lines, the 

 spectra consist of bright lines. The conclusion we arrive at from 

 this is, that these bodies do not consist of a white-hot nucleus, sur- 



