That said, there are irritating errors in the book.
Q. Please explain how to diagram a sentence.
A. First spread the sentence out on a clean, flat surface, such as an ironing board. Then, using a sharp pencil or X-Acto knife, locate the 'predicate,' which indicates where the action has taken place and is usually located directly behind the gills. For example, in the sentence: 'LaMont never would of bit a forest ranger,' the action probably took place in a forest. Thus your diagram would be shaped like a little tree with branches sticking out of it to indicate the locations of the various particles of speech, such as your gerunds, proverbs, adjutants, etc.
(2) Russia's proposal at the conference
The phrase in example (2) is talking about a kind of proposal. Russia's and at the conference tell us what specific proposal we're talking about. Proposal, therefore is the head word.
Intransitive—having one Subject, one Predicate.
Transitive—having one Subject, one Predicate, one Object.
A mixed sentence.—Def. 30, b.
A complex sentence—both simple and intransitive.
The last page of this volume contains a plug for another book of diagrams by the same publisher: Irish's Grammar and Analysis Made Easy and Attractive by Diagrams. Given the nature of the diagrams in Harvey's Grammar, I suspect that this diagram system was cribbed from Reed and Kellogg, with enough changes to avoid copyright problems.