When the first requisite of shelter has been obtained, the early builder cuts off the rough edges and carves upon the posts rude emblems of the natural objects he sees about him, and in doing this takes the first step in design and decoration. When wood is not abundant, he seeks a similar result in stone, and the treatment of each material gives rise to distinct principles of construction. The Greeks, who had marble-quarries of easy access, bridged over their posts or columns with straight lintels, capable of supporting the weight of the roof without danger of fracture. The Romans, who found their travertine difficult to handle, built their baths and palaces of brick, and, in seeking to connect their pillars and piers, adopted the round arch as a means of effecting this end, and this round arch was the main principle of Roman architecture. When, in due time, the pointed arch was found to combine great strength and beauty, this new method of building became the leading principle of Gothic art. So, according to each necessity, the different styles of architecture arose. When civilization increases the requirements of man, it is no longer possible to begin a rude construction, and alter it afterward to suit these needs; therefore it becomes necessary to consider beforehand all the elements required, and, in order to facilitate this consideration, drawing comes in as a simple means of placing before one all that enters into the proposed building. Therefore, in the study of architecture four divisions of the art must be considered, namely: The construction of buildings with various materials, the appropriate proportions of the same, their representation by draughtsmanship and their history in various times and among various peoples. It will be readily understood that each of these divisions embraces a wide scope individually, and yet no one can be separated from the others without affecting the result as a whole. It is proposed, therefore, to review briefly the history of this art, and the causes which have affected it, in order that, knowing the reasons which led to the formation of each style, the student may follow its study with the practical understanding and logical inference which lead to the best results. * * * * * The question of which country furnished the first or earliest period of approach to civilization in the building of monuments or habitations has been, and is likely to be, an open one for some time to come. Speculative discussion on this point can serve no end of importance to architects; it interests more especially the historian and antiquarian. Consequently we will, for the sake of convenience, glance over the periods of architecture in the following order: