Climate will necessarily operate a considerable effect upon the external arrangements of architecture. According to the latitude of the situation, buildings will be contrived to admit or exclude the sun, to give shelter from biting cold, or to secure against scorching heat, or merely to yield shade, without immediate reference to either extreme. All these, however, will not affect the internal harmonies or proprieties of the constituent parts. Climate, therefore, is only modifying, not creative, as the two preceding causes; it may suggest composition, but hardly design; for, with the exception of the pointed or flat roof, according to the humidity or dryness of the atmosphere, consequently the angular pediment surmounting the horizontal lines of the entablature, little of real form or order has been added, or materially influenced, by climate. This cause, however, has given rise to, or permitted, many picturesque combinations. Purpose, besides the constitutional effects upon the science already described, necessarily occasions the various classes under which the labours of the architect may be arranged. Architecture, by this principle, is separated into two grand divisions--Civil and Military. The former of these, from its greater variety of purpose, is further subdivided into subordinate heads, namely, placing each in the order of its probable antiquity, Sacred, Monumental, Municipal, and Domestic. These modifications of purpose do not, indeed, give novel principles, nor do they affect any of the conclusions already explained; they have only, though strongly, influenced the practice of the art. In presenting an abstract of the history of the science of Architecture, then, it is not requisite to dwell particularly upon these divisions, nor to be guided by them in the future arrangement of our matter. But as we may occasionally revert, by a passing word, to the obvious distinctions which are thus perceived, a short explanation, especially as several scattered particulars of very early times can thus be properly assembled, will here be useful. _Sacred Architecture_ is a term sufficiently expressive of its own import. It was the primitive effort of the present race of man; the first impress of his existence left upon the soil, yet moist from the waters of the deluge, was the erection of an altar; and the noblest evidence of his most accomplished skill has been a temple: ----'His greatest ornament of fame, And strength, and art.' From the 'altar builded by Noah,' how interesting to follow out the effects of one uncontrollable, but, when unguided, erring sentiment in the steadfast piles--'works of Memphian kings,' in the glorious proportions of Greece, where ----'Doric pillars, Cornice, and frieze, with bossy sculptures graven,'