Final answer:
The sentence 'Great works are performed not by strength but by perseverance' has 'works' as the main subject, a passive construction in the predicate 'are performed,' and a compound prepositional phrase that contrasts 'strength' and 'perseverance' as the means of performing the works.
Step-by-step explanation:
The sentence 'Great works are performed not by strength but by perseverance' can be diagrammed to identify its grammatical structure. The subject of the sentence is 'works,' which is modified by the adjective 'Great.'
The predicate is 'are performed,' indicating the action taken by the subject. This predicate is a passive construction, where 'works' is the receiver of the action 'performed.' The phrase 'not by strength but by perseverance' is a compound prepositional phrase acting as an adverb, telling us how the works are performed.
'Strength' and 'perseverance' are objects of the prepositions 'by' which, in this case, contrast the means by which the works are performed. In diagramming, they would fall under the verb 'are performed,' with a line separating 'not by strength' and 'but by perseverance' to show the contrast.