Indeed, Big Ben is the name given to the largest of the clock's bells and is the one that sounds on the hour. The clock itself is known, somewhat unimaginatively, as the 'Great Clock of Westminster'. The 320 ft. clock tower within which Big Ben, (and his smaller siblings), resides at the north end of the Houses of Parliament is St. Stephens Tower. The clock has four faces and beneath each is a latin inscription:

DOMINE SALVAM FAC REGINAM NOSTRAM VICTORIAM PRIMAM
-
"'Lord save our Queen Victoria the First"

The clock in St. Stephens Tower was commisioned in 1844, whilst the Houses of Parliament was being constructed. When Big Ben was cast, in 1858, it weighed approximately 13.5 tons and took 20 days to completely solidify and cool. Big Ben needed 16 horses, brightly decked out in ribbons, to pull it on a trolley through London on its short journey from the Whitechapel Bell Foundry to its new home.

Big Ben, first sounded across the rooftops of London on May 31st, 1859. However, disaster 'struck', (pardon the pun), some two short months later when Big Ben cracked. The cause, a hammer that was twice the specified weight, was replaced but it was three years before Big Ben once again rang out. He had been repaired and repositioned to offer a new striking surface to the hammer.

Big Ben is named after the Chief Commissioner of Works, Sir Benjamin Hall, who was in charge of such 'public works' at the time.


References

http://www.whitechapelbellfoundry.co.uk/bigben.htm