The abecedarian is an ancient poetic form guided by alphabetical order. Generally each line or stanza begins with the first letter of the alphabet and is followed by the next, until the final letter is reached. The earliest examples are Semitic and often found in religious poetry. The form was most used in ancient cultures for sacred compositions, such as prayers, hymns, and psalms. There are numerous examples of abecedarians in the Hebrew Bible; one of the most highly regarded is Psalm 118. Abecedarian poems are now most commonly used as mnemonic devices (a rhyme or phrase to help meorise) and word games for children. In Forché’s forty-seven page poem, "On Earth," she adheres to a rigorous form in which alphabetical order guides not only the stanzas, but also the words themselves. For example, she writes: "languid at the edge of the sea lays itself open to immensity leaf-cutter ants bearing yellow trumpet flowers along the road left everything left all usual worlds behind library, lilac, linens, litany." A form derived from the abecedarian is the acrostic, which spells out names or words through the first letter of each line. The intent of the acrostic is to reveal while attempting to conceal within the poem. William Blake addresses the despairs of the plague in the poem London, telling the reader how he listens to everyone’s pain while wandering along the Thames River. Blake uses an acrostic in the third stanza emphasize the horrifying sounds: "How the Chimney-sweeper's cry Every blackning Church appalls; And the hapless Soldier's sigh Runs in blood down Palace walls."