The excerpt describes a moment when Jonathan experiences a change in his physical state after coming into contact with the "darkling." Here's a breakdown of the text:
"For a moment Jonathan grew heavy; contact with the darkling had robbed him of his midnight gravity."
This sentence indicates that upon touching the "darkling," Jonathan's body became heavy, as if he lost his usual sense of weight or gravity. The term "darkling" likely refers to some sort of mysterious or supernatural creature.
"He fell toward the ground, but as the icy touch of the creature's flesh faded, Jonathan's body lightened again."
After making contact with the "darkling," Jonathan started to fall toward the ground due to the sudden heaviness. However, as the "darkling" moved away or the contact ceased, the icy touch of the creature's flesh faded, and Jonathan's body became light again, returning to its usual state.
This excerpt seems to describe a supernatural encounter or a moment involving magical elements, as the effect on Jonathan's body defies the laws of conventional physics. It creates a sense of mystery and wonder, leaving readers intrigued about the nature of the "darkling" and its impact on Jonathan.