Ericsson was essentially a designing rather than a constructing engineer.  His genius lay in new adaptations of the principles of mechanics or in new combinations of the elements of engineering practice in such way as to further the purposes in view.  His mode of expression was the drawing-board.  While he wrote vigorously and well, and while he was a frequent contributor in later years to scientific literature, especially on the subject of solar physics, yet his best and natural mode of expression was the graphical representation of his designs on the drawing-board.  Forms and combinations took shape in his brain and were transferred to the drawing with marvellous speed and skill.  Those who have been associated with him bear testimony that the amount of his work was simply astounding, and that only by a combination of the most remarkable celerity and industry could they have been accomplished.

These drawings were furthermore so minute in detail and so accurate in dimension that as a rule he did not find it necessary to give further attention to the matter after it had left his hands.  Of the many parts of a complicated mechanism, one could be sent for construction to one shop and another elsewhere, all ultimately coming together and making a harmonious and perfectly fitting whole.  In no other way could such astonishing speed in the detailed construction of the “Monitor” and other vessels of her type possibly have been made; and the fact that such speed in construction was obtained, and largely in this manner, is by no means the least impressive of the many evidences of Ericsson’s genius as a designer.

The designs once completed on the drawing-board, however, Ericsson’s interest in the work ceased in great measure, and as a rule he paid but little attention to constructive details, and took but slight interest in the completed whole.  Thus he is said to have visited his “Destroyer” but once after she was built, and then simply in search of his assistant.  He also declined an invitation from the Assistant Secretary of the Navy to visit Hampton Roads and inspect the “Monitor” immediately after her fight with the “Merrimac.”  He seemed to have no curiosity to inspect his work after it had left his hands, or to receive a report as to the practical working of his designs.  This shows a peculiar lack of appreciation of the value of intimate contact with constructive and operative engineering work.  No one could hope to avoid errors, or to realize by drawing-board alone the best possible solution of engineering problems.  Ericsson wilfully handicapped himself in this manner, and might unquestionably have more effectively improved and perfected his ideas had he been disposed to combine with his designs at the drawing-board practical contact with his work as constructed.

His work was all done in his office at his house.  For the last twenty-five years of his life he lived at 36 Beach Street, New York, where he wrought every day in the year, and often until far into the night.  His office contained, beside his drawing-table and other furniture, a long table, on which at times, when overcome by fatigue, he would stretch himself and take a short nap, using a dictionary or low wooden box for a pillow.