Going with Frank's suggestion of trying to find the book in a library, I checked on WorldCat (global catalog, of participating libraries, provided by OCLC.org). The only book that they have by that author is about Grahams.
https://www.worldcat.org/search?q=Ruth+Cleghorn+Ker&qt=results_page
That book is in New Brunswick Canada. If that is where Ms. Ker is located than her home library or genealogy society might have a copy of the book you want.
Having this information, if you go to a library will impress them with your prowess; and, make them think of other avenues to help (including a more advanced search).
Good luck