Theory:

The poetry of earth is ceasing never:
On a lone winter evening when the frost
Has wrought a silence, from the stone there shrills
The cricket’s song, in warmth increasing ever,
And seems to one in drowsiness half lost;
The grasshopper’s among some grassy hills.
Explanation:
 
The poet repeats the main theme of the sonnet that the voice of the earth never comes to an end, even during the winter.
 
The line "the frost has wrought a silence"- is an instance of personification. Frost is personified as a person who brings silence in his wake. Unlike summer, winter is presumed as a time of inactivity: trees look barren, birds have migrated, and people take sanctuary inside their homes. However, the poet says that the silence is broken through the song of crickets, whose music gets only louder with time. When the small fragments of snow bring silence, one can hear the voice of the cricket's song from the stone.
 
"The Crickets song, in warmth, increasing ever" is alluded to as a metaphor since this line states that the cricket's song will remind you of summer and its warmth during the winter when it's cold.
 
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Cricket sings during winter
 
The poet says that the person who is half-lost in drowsiness would think that it is the grasshopper that is singing in some grassy hills. The cricket's song sounds similar to that of a grasshopper from some grassy hills during the summer. Hence, people experiencing winter might be reminded of the warmth of the summer. In this way, nature keeps itself alive, merry-making and singing, irrespective of the kind of weather people face.
 
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Cricket's song is similar to that of a grasshopper
 
Meanings of difficult words from the poem "On the Grasshopper and Cricket":
 
No
Words
Meanings
1.
wroughtbrought about
2.
shrillsound is high pitched and sharp
3.
ceasingto come to an end; stop
4.
warmththe sensation of moderate heat
5.
drowsinessa feeling of being sleepy and lethargic; sleepiness
6.
lonebeing alone; standing by itself or apart
7.
frosta thin layer of ice on a solid surface
Reference:
National Council of Educational Research and Training (2008). Honeydew. On the Grasshopper and Cricket (pp. 118-119). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.