Joseph Rydings (1934), Country Walks in Many Fields; Being Certain Choice Annals of The Paterson Rambling Club. Paterson, NJ: Press of the Morning Call.
There seems to have been a modern (POD?) $ 15 reprint of this 338-page book by the Passiac County Historical Society, but the first edition seems pretty common. The Society website was last updated 2009, and they have blanked the Publications page. The book’s Contents list is available here. The book does not appear in Joshi’s Comprehensive Bibliography, and it’s possible no Lovecraftian has ever looked through it to glean anything that might relate to Morton and the Lovecraft circle.
The Paterson Rambling Club was apparently where members of the Lovecraft circle took refuge, after Lovecraft had left New York. Paterson was where James F. Morton was curator of the Paterson Museum.