It is unfair to attempt the explanation of this system without accompanying drawings, but it may be stated that the air, drawn by fan-blowers from the heated portion of the fire-room, is forced through a passage into the ash-pit and furnace, a portion of the current being directed by an interposed plate through the holes in the furnace frame. By the agency of a double row of holes the greater portion of the air which enters the furnace passes around the frame, thence through other apertures to the space between the furnace door and lining, and finally to the furnace through the space between the lining and furnace frame. The supply of air when firing or hauling ashes is shut off by a damper. APPENDIX II.[61] THE QUESTION OF TYPES. The following letter appeared in the _Times_ (London) of April 4, 1885: “SIR,—May I request the favor of space in the _Times_ in which to comment upon the opinions recently expressed by Sir Edward Reed and other writers respecting the designs of the _Admiral_ class of ships in the Royal Navy, and the four central-citadel ships which were laid down subsequently to the _Inflexible_? “Having been closely associated with Mr. Barnaby in the designing of all these ships, with the exception of the _Ajax_ and _Agamemnon_, I can speak with full knowledge of both the history and intentions of the designs. “Moreover, my share of the responsibility for the professional work involved in those designs remains, although my official connection with the constructive department of the Admiralty was severed years ago. It need hardly be added that the remarks which follow simply embody my own opinions, and that I write neither as an apologist for Mr. Barnaby nor as a champion of the ship-building policy of the Admiralty. “The sweeping condemnation which has been pronounced against the most recent English battle-ships is based upon the consideration of one feature only in their fighting efficiency, _viz._, the extent of the armor protection of their sides in the region of the water-line. There has been no discussion in the letters to which I have referred of the comparative speeds, armaments, or other qualities of the French and English ships. But the fact that the French ships are armor-belted from end to end, while the English ships have no vertical armor on considerable portions of the length at the region of the water-line, is considered by Sir Edward Reed so serious a matter that he says, ‘The French armored ships must in all reason be expected to dispose of these English ships in a very few minutes by simply destroying their unarmored parts.’