The estate’s stable is published — Merrill & Cutler, architects
The American Architect and Building News prints a heliotype plate: "Stable for Mr A. T. Atherton, Fairmount St, Lowell — Merrill & Cutler, Architects". A stone stable with a conical-roofed round tower, it is today’s carriage house at 222 Fairmount Street. No published design for the house itself has been found, so the architect of the house remains unrecorded.[sources]
What is uncertain: Whether Merrill & Cutler also designed the house is plausible but undocumented; the 1981 survey left the architect blank.