Matthew Poole and continuators on Genesis 6:15

15. And this is the fashion which thou shalt make it of : The length of the Ark shall be three hundred cubits, the breadth of it fifty cubits, and the height of it thirty cubits .

Or, This is the measure, or, the manner according to which thou shalt make it.

A just and regular proportion, the length being six times more than the breadth, and ten times more than the height. There is no need to understand this of Geometrical cubits, which are said to have contained nine ordinary cubits, nor of sacred cubits, which were an hands breadth longer than the ordinary, Ezek. 13. 13. Nor to suppose the stature of men at that time to have been generally larger, and consequently their cubit much longer. For the ordinary cubit consisting of a common foot and an half is sufficient for the containing of all the kinds of living Creatures and their provisions, which was to be put into the Ark, as hath been at large demonstrated by learned men. Nor is there any considerable difficulty in the point but what is made by the ignorance of Infidels, and aggravated by their malice against the Holy Scriptures. Especially if these things be considered; 1. That the differing kinds of Beasts and Birds, which unlearned men fancy to be innumerable, are observed by the Learned, who have particularly searched into them and written of them, to be little above three hundred, whereof the far greatest part are but small, and many of these which now are thought to differ in kind, in their first original were but of one sort, though now they be so greatly altered in their shape and qualities; which might easily arise from the diversity of their Climate, and Food and other circumstances, and from the promiscuous conjunctions of those lawless Creatures. 2. That the brute Creatures when they were enclosed in the Ark, where they were idle, and constantly under a kind of horrour and amazement, would be contented with far less provisions, and those of another sort, than they were accustomed to, and such as might lye in less room, as Hay and the Fruits of the Earth. God also who altered their natures, and made the savage Creatures mild and gentle, might by the same powerful Providence moderate their appetites, or if he pleased, have increased their provision whilst they did eat it, as afterwards Christ did by the loaves. So vain and idle are the cavils of wanton wits concerning the incapacity of the Ark for the food of so many Beasts. 3. That supposing the ravenous Creatures did feed upon flesh, here is also space enough, and to spare for a sufficient number of Sheep, for their food for a whole year, as upon computation will easily appear, there being not two thousand Sheep necessary for them, and the Ark containing no less then four hundred and fifty thousand solid cubits in it. But of this matter more may be seen in my Latin Synopsis.