Some industrious students however discovered that the entire book, including this sermon, is available on Google book search! I recommend the book to you. It includes Scougal’s Life of God in the Soul of Man which has had significant impact over the years in the lives of men such as Wesley, Whitefield and more recently John Piper (see the preface to The Pleasures of God).
This sermon is based on 2 Cor 2:16 where in discussing the weightiness of preaching the gospel Paul asks “Who is sufficient for such things?” Here are some quotes to allure you to read the whole thing.
“it [the gospel] proves a vital savor to those who receive and obey it, but a most deadly poison to all who reject and despise it.” p. 228
“And shall we undervalue the price of His blood, or think it a small matter to have the charge of those for whom it was shed? It is the Church of God we must oversee and feed; that Church for which the world is upheld, which is sanctified by the Holy Ghost, on which the angels themselves attend. What a weighty charge is this we have undertaken! And ‘who is sufficient for these things?’” p. 234
“But certainly the greatest and most difficult work of a minister is in applying himself particularly to the various persons under his charge; to acquaint himself with their behavior and the temper of their souls; to redress what is amiss and prevent their future miscarriages. Without this private work, his other endeavors will do little good.” p.241
“Now this supposes a great deal of care, to acquaint ourselves with the humors and conversation of our people; and the name of ‘watchmen’ that is given to us implies no less.” p.252