When I behold some curious piece of art,

 Or pretty bird, flower, star, or shining sun,

Pour out o’reflowing glory:  oh!  my heart

 Aches seeing how my thoughts in snick-snarls run.

 But all this glory to my Lord’s a spot

 While I instead of any, am all blot.

Paraphrase: I am taken by many lesser glories, a work of art, beauty in nature (it should be noted there here is an example of nature being seen as beautiful by a man living on the edge of a dangerous wilderness — and before the Romantics), my heart is taken with the glory. My thoughts become overwhelmed with these lesser sights. But all such glory is nothing compared with God’s glory; while I am on who is marked by the utter absence of glory.

Snick-snarl: What a wonderful phrase. An essay entitled, ” The Lincolnshire Dialect in the Eighteenth Century” defines it as follows, “Snick Snarl, a, curling up (particularly burnt leather). [Wright defines as “a tangle in thread etc.”].” http://www.cantab.net/users/michael.behrend/repubs/lincs_dialect_18c/pages/main.html It’s one of the words that sound like its meaning.

Scansion:  The third and fourth line have a jerky movement which slows the reading and forces attention on the meaning: The first word “pour” has an uncertain weight. It could be read POUR out or Pour OUT.  The phrase “o’reflowing glory: oh!”, while regular o’reFLOWing GLORy, OH, has an interesting effect based upon the assonance the repetition of O, including OR, twice. It is impossible to say the phrase quickly. One must to even say the words. It is made more difficult to pronounce because the scansion is regular, “overflowing glory” would much easier and quicker.

Another interesting movement runs from line 3 to 4, “OH! my HEART/ACHES, the emphasis thus thrown on “aches”.

Biblical Allusion: While there is a generic allusion to the beauty of God and stain of sin on man [by the way, a study should be made of whether Taylor, who was a friend of Jonathan Edward’s father, communicated any of this doctrine of glory to Edwards — who was overwhelmed with God’s glory], there appears to be a specific allusion to Hebrews 1:

Hebrews 1:1–3 (AV)

¹ God, who at sundry times and in divers manners spake in time past unto the fathers by the prophets, ² Hath in these last days spoken unto us by his Son, whom he hath appointed heir of all things, by whom also he made the worlds; ³ Who being the brightness of his glory, and the express image of his person, and upholding all things by the word of his power, when he had by himself purged our sins, sat down on the right hand of the Majesty on high;

The Greek which underlies the English is

Hebrews 1:3 (SBLGNT)

³ ὃς ὢν ἀπαύγασμα τῆς δόξης καὶ χαρακτὴρ τῆς ὑποστάσεως αὐτοῦ, φέρων τε τὰ πάντα τῷ ῥήματι τῆς δυνάμεως, διʼ αὑτοῦ καθαρισμὸν τῶν ἁμαρτιῶν ποιησάμενος ἐκάθισεν ἐν δεξιᾷ τῆς μεγαλωσύνης ἐν ὑψηλοῖς,

Which has the idea of effulgence or radiance. If there is an “overflowing glory” and effulgence of glory in the creature, how much more glory in the Creator.