No authority on this subject can be equal to the Scriptures; and there we find the number seven always used as a number of greater importance than any other;--the six days of creation, and the seventh day of rest, from that time more or less observed as a holy or superior day, by divine command,[8] is the first and one of the most remarkable instances: I need merely mention the seven clean animals which Noah was commanded to take into the ark, the seven plagues, seven years of famine and of plenty, and that more than two hundred other instances occur in the Old Testament. In the New the number seven occurs still more remarkably: as seven golden candlesticks, seven churches, seven angels, and seven spirits of God. I need scarcely go further; but being able to adduce the opinions which have been avowed by the greatest naturalists that have ever lived, I rejoice to strengthen my own opinion by such high authorities. M. le Baron Cuvier, in a paper published in 1795, divided all invertebrate animals into six groups, the vertebrates forming the seventh.[9] Our eminent countryman, Mr. Kirby, observes: "The number five, which Mr. MacLeay assumes for one basis of his system, as consecrated in nature, seems to me to yield to the number seven, which is consecrated both in nature and in Scripture. Metaphysicians reckon seven principal operations of the mind; musicians seven primary musical notes; and opticians seven primary colours. In Scripture the abstract idea of this number is fulness, completeness, perfection. I have a notion, though not yet sufficiently matured, that Mr. MacLeay's quinaries are resolvable into septenaries."[10] Our own observation will speedily convince us, that most groups of animals with which we are tolerably well acquainted are divisible into seven; we shall never find the number greater, and when less, we shall invariably perceive that the deficiency exists in groups of which our knowledge is particularly limited, for the perfection of a septenary distribution of any particular group will depend entirely on our acquaintance with that group: thus the groups at present known by the names Mammalia, Aves, and Insecta, resolve themselves instantly into sevens. No ingenuity can frame eight good groups of either, and no scheme, however plausible, can reduce the number to sixes or fives. An attempt to reduce birds into five groups has been made in this country; I cannot do better than refer the reader to it as a triumphant confirmation of the predominance of the number seven.[11] The great Linnæus assigned to Mammalia seven orders, to Aves six, and to Insecta seven, in a system which, though capable of improvement in many of the orders, evidently points to the truth, and considering his limited means of reference, compared with what the naturalist now possesses, was a remarkable and magnificent monument of human talent.[12] [8] Genesis ii. 3.