ILLUSTRATIONS. 



FIG. PAGE 



1. Arrangement of candle, prism and eye 2 



3. Use of the simple spectroscope ... ... ... ... 3 



3. A continuous and a discontinuous spectrum ... ... ... G 



4. Use of a circular and line slit ... ... ... ... ... 7 



5. Observation of a flame with ordinary spectroscope ... ... 7 



6. Steinheil spectroscope ... ... ... ... ... ... 8 



7. Angstrom's grating spectrometer ... ... ... ... 9 



8. Spectra of barium and iron contrasted ... ... ... 9 



9. Fluting of carbon 10 



1 0. Fluting of magnesium ... ... ... ... ... ... 10 



1 1 . The " series " of cleveite gases ... ... ... ... 11 



12. Fraunhofer's solar spectrum ... ... ... ... ... 15 



1 3. A stellar spectroscope ... ... ... ... ... ... 16 



14. Spectroscope attached to a telescope for sun observations ... 21 



15. First method of spectroscopic work 21 



16. New method of using a lens 22 



17. Long and short lines of strontium and calcium ... ... 23 



18. Long and short lines of sodium ... ... ... ... 24 



19. Spectrum of a sun-spot... .... ... ... ... 25 



20. Spot and prominence lines contrasted... ... ... ... 26 



21. Different rates of motion registered by different iron lines ... 27 



22. Comparison of chromospheric and test spectra 40 



23. Spectrum of chromosphere contrasted with Fraunhofer lines 40 



24. Temperature curve ... ... ... ... ... ... 47 



25. Comparison of the spectrum of a Cygni with enhanced 



metallic lines 49 



26. Comparison of the spectrum of a Cygni and chromosphere ... 53 



27. Map of chemical substances present in stars of different tem- 



peratures ... ... ... ... ... ... ... 62 



28. Comparison of the spectra of Sirius and a Cygni ... ... 69 



29. Comparison of the spectra of Procyon and y Cygni ... .. 69 



30. Simple flutings of nitrogen 84 



