In this story, I can see many figures of speech. Here are two of them.
First, there is hyperbole. This is a figure of speech where a speaker exaggerates some quality or characteristic of some thing that he is describing. In this story, we see the line
such a fresh bubbling spring that it seemed never to have sparkled for any wayfarer but David Swan
The speaker is exaggerating how pretty the spring was so as to show how thirsty Swan was.
Then there is personification -- this is when the writer gives characteristics of living things to inanimate objects. There are several of these in the following lines:
The spring murmured drowsily beside him; the branches waved dreamily across the blue sky overhead; and a deep sleep, perchance hiding dreams within its depths, fell upon David Swan.