Sentence:  In the Vatican Library is a vase of terra cotta, on whose upper part we see delineated the sun and moon, in a <WSD>quadriga</WSD>, which proceeds forward [travels, voyages, fulfils its course] upon a ship. ... Both these deities stand in a <WSD>"quadriga</WSD>", which indeed is the vehicle proper to the sun, insomuch that the Rhodians every year threw into the sea a <WSD>"quadriga</WSD>", dedicated to this divinity. 
Meaning of the word marked with <WSD> tags:  A Roman racing chariot drawn by four horses abreast.