Final answer:
The theme that magic can be lost to industry is best revealed in the lines 18-20 of the passage, that magic can be lost to industry, showing the strain of life in offices and factories and the yearning for the mystical elements of nature that are replaced by industrial and mechanical concerns.
Step-by-step explanation:
The theme that magic can be lost to industry is best revealed in the lines 18-20 of the passage:
But one of the crowd stepped from the throng today
With pointed brows and I heard him say
"Out of the meadows and rivers and trees
We fauns and many companies
Of nymphs have come and we are these
These people, each upon his way,
Looking for work, and working for pay—
These lines suggest that the fauns and nymphs, symbolic of magic and nature, have become a part of the crowd of people who are focused on industry and work. The speaker longs for the presence of these magical creatures but realizes that in the modern world, the pursuit of industry has caused the loss of magic.