This is from The Book of Sun-Dials by Mrs. Alfred Gatty [aka Margaret Scott Gatty], which you can read online at this University of Pennsylvania website.
In Aeternos Dies
Ista velut tacito cursu dilabitur umbra,
Transit in aeternos sic tua vita dies.
The vocabulary is keyed to the DCC Latin Vocabulary list. There is only one word in this poem that is not on the DCC list:
dīlābor, dīlābī: fall apart, decay, melt away
aeternus -a -um: everlasting, eternal
cursus -ūs m.: course, advance
diēs diēī m./f.: day
in: in, on (+ abl.); into, onto (+ acc)
iste ista istud: that, that of yours; adv. istīc or istūc: over there; istinc: from over there
sīc: in this manner, thus; sīc . . . ut: in the same way as
taceō -ēre -uī -itum: be silent; tacitus -a -um, silent
trānseō -īre -iī -itum: go across
tuus -a -um: your
umbra -ae f.: shade, shadow
velut: even as, just as
vīta -ae f.: life
