By the turn of the nineteenth century, John Lubbock was able to attribute the site to the Bronze Age based on the bronze objects found in the nearby barrows. Radiocarbon dating of the site indicates that the building of the monument at the site began around the year 3100 BC and ended around the year 1600 BC. This allows the elimination of a few of the theories that have been presented. The theory that the Druids were responsible may be the most popular one; however, the Celtic society that spawned the Druid priesthood came into being only after the year 300 BC. Additionally, the Druids are unlikely to have used the site for sacrifices, since they performed the majority of their rituals in the woods or mountains, areas better suited for "earth rituals" than an open field. The fact that the Romans first came to the British Isles when Julius Caesar led an expedition in 55 BC negates the theories of Inigo Jones and others that Stonehenge was built as a Roman temple. The classical Greek writer Diodorus Siculus (1st century BC) may refer to Stonehenge in a passage from his "Bibliotheca historica". Citing the 4th-century BC historian Hecataeus of Abdera and "certain others", Diodorus says that in "a land beyond the Celts" (i.e. Gaul) there is "an island no smaller than Sicily" in the northern sea called "Hyperborea", so named because it is beyond the source of the north wind or "Boreas". The inhabitants of this place chiefly worship Apollo, and there is "both a magnificent sacred precinct of Apollo and a notable temple which is adorned with many votive offerings and is spherical in shape." Some writers have suggested that Diodorus' "Hyperborea" may indicate Great Britain, and that the spherical temple may be an early reference of Stonehenge. Christopher Chippindale commented that "This "might" be Stonehenge, but the description is short and vague, and there are discrepancies = the climate of the Hyperboreans is so mild they grow two crops a year." Aubrey Burl noted that other parts of Diodorus' description make it a poor fit for Stonehenge and its neighbourhood. Diodorus also says that in that area Apollo (meaning, the Sun or the Moon) "skimmed the earth at a very low height". However, both the Moon and the Sun are always seen far above the horizon at the latitude of Stonehenge; only 500 miles farther north can they be observed to remain near the horizon.