Jefferson designed the wind compass on the ceiling of the Monticello portico; it is attached to the weather vane directly above it on the roof. The portico clockface reflects the time on the Great Clock in the entrance hall interior of the house. The Great Clock with its two faces was considered to be sophisticated technology for its time. Unlike the Great Clock of the interior, the portico clockface does not have a minute hand. When Jefferson was living on the plantation, a bell rang on the hour and could be heard for approximately five miles. Jefferson wanted everyone on the plantation to be on the same time schedule.