Cast-iron beams had been used for upright supports for a quarter of a century. There had even been some experimenting with wrought iron, notably by Princeton University, which had bought railroad rails from the Trenton works for use in Old North Hall, but none were available that were large enough for the building Mr. Cooper had in his mind. With characteristic enterprise stimulated by the inventive spirit that motivated much of his activity, Mr. Cooper ordered "the boys" at Trenton (his son Edward and his son- in-law Abram S. Hewitt) to direct their efforts to rolling beams twice as deep as they had previously attempted.

Rolls were imported from England at a cost of some $75,000 and the Trenton staff set to work, at first under William Barrow, the foreman who soon worked himself into his grave, and later under Hewitt's brother Charles, who completed the task. After a total expenditure of $150,000, beams twenty feet long and seven inches deep were finally produced in 1853. The building of The Cooper Union could now go forward.

Charles Hewitt's description of his solution to the problem may be of interest. "A three high mill was placed vertically instead of horizontally," he wrote, and "additional horizontal rolls were provided to operate where the vertical rolls came together at the top."  The machinery was "what is known as the universal mill, now in use for rolling plates and shapes. It was so far as I know the first universal mill that was ever built."

The cornerstone ceremony was a merry occasion. Mr. Cooper opened the proceedings by reading the following address:
  
"Mr. Mayor, allow me to thank you for your kind cooperation in laying this stone, where I trust it will rest forever, with its contents, on the foundation of eternal truth. I design to raise on this foundation a structure to be forever devoted to the cultivation and spread of just and necessary knowledge, until all shall know, from the least to the greatest, those things which make for their peace.
  
"On this foundation—in this building—I trust that thousands yet unborn will here receive the inspiration of truth in all its native power and beauty, and find in it a source of inexpressible pleasure in spreading its transforming influence throughout the world.
  
"The great object that I desire to accomplish by this institution is to open the avenues of scientific knowledge to the youth of our country, so unfolding the volume of Nature that the young may see the beauties of creation, enjoy its blessings, and learn to love the Author from whom cometh every good and every perfect gift. My heart's desire is to aid the rising generation to become so thoroughly acquainted with the works of Nature and the great mystery of their own being, that they may so feel and understand those immutable laws that are designed in infinite wisdom; laws which are constantly operating for our good, and so governing the destinies of worlds and men that it is our highest wisdom to live in strict conformity to those laws.

"I design to make the Institution that is to rest on these walls contribute in every way possible to aid the efforts of youth to acquire that kind of useful knowledge which will enable them to find and fill valuable places where their capacity and talents can be employed with the greatest possible advantage to themselves and the community in which they live.

"My design is to place this institution in the hands, and under the control, of men who will forever devote it in the most effectual manner to the moral, mental and physical improvement of the rising generation; to aid and encourage the young to improve and better their condition. I design to provide for a continued course of night and day lectures and discussions on the most useful and practical sciences, to be open and free to all who can bring a certificate of good moral character from parent, guardian or employer, feeling the great necessity for the application of science to supply the moral, mental and physical wants of mankind, and believing that the science and philosophy of Government should be applied to the uses and purposes of elevating our race, by giving real security and value to all the varied forms of human labor.