Around 1907 Morgan apparently consented to pose for the Austrian-born artist Emil Fuchs, a successful portrait painter working in London and New York. In his autobiography, Fuchs explained that he declined to proceed with the portrait because “the gulf between [Morgan] and the mere outside world was immeasurable” and “I should not have been able to approach close enough to penetrate behind that concealing mask.” For Fuchs, however, the encounter led to a welcome opportunity:

His librarian obtained permission for me to sketch the interior of his treasure-house at night. This was a task to my liking. To be surrounded by the art of bygone days in the witching hour of the night, gave me far more pleasure than the dinner parties I thus missed.

In early 1904, two years after Morgan had commissioned the Library, McKim and his partner William Rutherford Mead were finally ready to present the interior designs. “The proposition we desire to submit for your consideration,” McKim wrote to his client, “is the result of months of study, & I trust in its general policy will commend itself as dignified and appropriate to the purposes of a library.”

William Mitchell Kendall, one of the architects working on the project with McKim, created this elevation of the Rotunda, or “main hall.” He began to articulate the decorative details that would ultimately distinguish the completed space.

While McKim designed the Library with the aim to draw the eye upward, he was equally attentive to the ground below. This is one of several surviving drawings that record the firm’s careful planning for the pavement of the Rotunda, which pays homage to the sixteenth-century Casina Pio IV (Villa Pia) in the Vatican Gardens. McKim asked the sculptor Waldo Story, who was living in Rome, to scout antique marble samples of a variety of hues, with a particular focus on securing the central disc of deep-red-purple porphyry.

William J. Sayward was one of the architectural drafters at McKim, Mead & White assigned to work closely with contractors on the Morgan Library project. He created this intricate drawing for the ornamentation of the Rotunda’s dome, which would incorporate a central skylight, or oculus (here marked “plate glass”). The artist H. Siddons Mowbray, who was engaged to create the painted decoration, would refine these designs for the roundels and other paintings, taking into account that “the ceiling is pierced by light.”

This watercolor rendering complements the more technical elevation of the proposed design for the Rotunda seen nearby. The color scheme for the semicircular dome of the apse would ultimately be simplified to a solid white with blue and gold accents. Like many elements of the Library, it was adapted from a sixteenth-century Roman source, in this instance the garden loggia of the Villa Madama.

The artist H. Siddons Mowbray was engaged to create the reliefs, which depict Roman mythological figures and allegorical representations of nature. Mowbray completed the modeling on-site, climbing up and down the scaffolding many times to ensure that his creations would be effectively illuminated by the Rotunda’s skylight.

As they developed this design for the dome of the Rotunda, McKim, Mead & White turned to the ceiling frescoes Raphael had created for the Vatican’s Stanza della Segnatura in the early sixteenth century. It was an appropriate (if grandiose) choice: Pope Julius II had used the room as a library and private office.

In 1904 McKim engaged the American artist H. Siddons Mowbray to execute the twelve paintings that would be inserted into the Rotunda ceiling. “It will necessitate a period of study in Rome, of examples of decoration of the same period,” Mowbray told McKim.

Mowbray made this copy of a portion of Raphael’s frescoed ceiling in the Stanza della Segnatura in the Vatican, making some adjustments to the colors of the borders. For the four roundels in the dome of the Rotunda of Morgan’s Library, Mowbray would adapt Raphael’s work and portray female personifications of the humanist ideals of art, science, philosophy, and religion.