Roxana CazanAltoona, Pennsylvania, United States At the Natural History Museumin Salt Lake City, I am promised“the assemblage of nature’s ultimatemachine,” its precise lurking,one foot crossing the Silurian,its simian lurch trapped behindshatterproof glass.I zigzag through the dinosaur world,the tender bend of boney necks,their petrified savagery mintedinto thick layers of shale,their swift death on display.When I pass…