The abundances of the elements.

For the immediate cosmic environs, there are three traditional sources of element abundance data, including chondritic meteorites, the solar atmosphere, and a certain type of average of stars near the sun. Cosmic ray material, or at least the particles that were accelerated to very high energies, includes contributions from great distances in the Galaxy, and perhaps from outside the Milky Way system itself. Problems in the determination of solar system abundances are discussed together with some factors affecting the profiles of spectral lines, the abundances of some elements in the solar atmosphere, young stars and the interstellar medium, the helium to hydrogen ratio, the helium isotopes, and abundances of light elements in the Galaxy and in neighboring galaxies.