(Fig. 11) is a double firecock, as laid down in Her Majesty's Dockyards.
Fig. 11. Double Firecock, used at the Royal Dockyards.
It will be observed, that the short piece of pipe between the main and this firecock is not curved to the current of the water, but merely opened a little; this is done with a view of increasing the supply by steam power, and as the steam engines are, in most cases, situated in a different direction from the tanks or reservoirs, therefore the curve that would have assisted the current in one direction would have retarded it in the other. It has been objected to these firecocks, that the opening does not run through the centre of the key, therefore only one side of the key covers the opening in the barrel, while in the common firecock both sides are covered.
Fig. 12. Double Firecock, used at the British Museum.
(Fig. 12) is a double firecock, as laid down at the British Museum.