Book found in antique desk

My dear aunt collected antique furniture and houses. She purchased the Carmelite nunnery in Carmel Valley near Del Mar California, refurbished it and lived in it. The nuns ran Mercy Hospital, San Diego Ca. and built the house in 1905. A Henry Clay,(not THE) desk she purchased was also in the house. Upon her passing this book was discovered in that desk, reputed to have been made somewhere in the 1800's. I would like to verify it's age if possible. TITLE: THE SEASONS,
by James Thomson...."with his last CORRECTIONS, ADDITIONS and IMPROVEMENTS. "A NEW EDITION., London, 1797. 161 pages with illustrations and a foreward "The Life of JAMES THOMSON, a - xii.

thanks for any help

james