Type G (Sun type). Numerous metallic lines together with relatively faint hydrogen lines.
To this class belong the sun, Capella, α Centauri and other bright stars.
Type K. The hydrogen lines still fainter. The K-line attains its maximum intensity (is not especially pronounced in the figure of [plate III]).
This is, next to the A-type, the most numerous type (1142 stars) among the bright stars.
We find here γ Andromedæ, β Aquilæ, Arcturus, α Cassiopeiæ, Pollux and Aldebaran, which last forms a transition to the next type.
Type M. The spectrum is banded and belongs to Secchi's third type. The flutings are due to titanium oxide.
Only 190 of the stars visible to the naked eye belong to this type. Generally they are rather faint, but we here find Betelgeuze, α Herculis, β Pegasi, α Scorpii (Antares) and most variables of long period, which form a special sub-type Md, characterized by bright hydrogen lines together with the flutings.
Type M has two other sub-types Ma and Mb.
Type N (Secchi's fourth type). Banded spectra. The flutings are due to compounds of carbon.
Here are found only faint stars. The total number is 241. All are red. 27 stars having this spectrum are variables of long period of the same type as Md.