Another stratum... is that of Coma Berenices, as I shall call it... It has many capital nebulae very near it; and in all probability this stratum runs on a very considerable way. It may, perhaps, even make the circuit of the heavens... the direction of it towards the north lies probably with some windings through the Great Bear onwards to Cassiopeia; thence through the girdle of Andromeda and the northern Fish, proceeding towards Cetus; while towards the south it passes through the Virgin, probably on to the tail of Hydra and the head of Centaurus.
It is worth noting that whilst William Herschel in The Construction of the Heavens (Herschel 1785) clearly observed the presence of clusters of nebulae (galaxies) in the night sky, it still remained an uncertainty at this time whether the nebulae resided within or without or own galaxy, the milky way. Indeed, although Thomas Wright, Immanuel Kant and Johann Lambert had postulated that the nebulae were separate island universes outside the Galaxy (see Harrison 2000, page 66 for a discussion), it was still being debated in the 1920s as to whether or not this was the case, with Heber Curtis championing the case for the extragalactic theory (see Rowan-Robinson 1999, page 41). It was not until Edwin Hubble began his systematic measurements of the distances to galaxies with the 100-inch telescope at Mount Wilson, using the relation found by Henrietta Leavitt (Leavitt 1908) between the periodicity of Cepheid variable stars and their luminosity, that the case was really settled (see Hubble 1936).
The phenomenon of clustering of galaxies was not really appreciated fully until the work of Fritz Zwicky and George Abell and the systematic cataloguing of clusters (Zwicky et al. 1961-1968, Abell 1958). Given the relative youth of the subject a remarkable amount of data and knowledge of clusters of galaxies and phenomena associated with them has been accumulated. However, one should bear in mind the nascence of the field, particularly at wavelengths other than visible, and the considerable array of unanswered questions therein. This monograph is an attempt to answer some of these questions with special attention paid to the evolution of clusters of galaxies.
This chapter introduces the modern picture of a cluster of galaxies and presents an introduction to theories of structure formation, of both clusters of galaxies as a whole and of galaxies within clusters. Following this, chapter 2 offers a brief introduction to the instrumentation used in obtaining data for this thesis. The first part of chapter 3 explains how studies of the X-ray properties of clusters can be used to study the evolution of clusters of galaxies. The remainder of chapter 3 presents a detailed analysis of the X-ray luminosity function of a sample of moderately high redshift (
-0.6) clusters.
Following this chapter 4 introduces infrared and optical astronomy of galaxy formation and evolution. The next two chapters present detailed studies of the 
band luminosity function of three of the most massive high redshift clusters of galaxies known and the colour-magnitude relation of one of them. Finally the conclusions and discussion of the evolution of clusters of galaxies are presented in chapter 7.
First we begin with a brief description of a model of a cluster of galaxies and its constituent parts.