Sir,--The account lately given in your paper of the explosion of the powder magazine at the Royal Military Barracks at Dorchester induces me to ask your permission to make public, through your columns, a method of storage by which all such explosions may be rendered absolutely impossible. The plan is briefly as follows:--The powder is to be stored in hexagonal zinc or copper drums of uniform, convenient size, and with water-tight easily removable covers. These drums are to be stored in shallow, open, brick-and-cement tanks, kept full of water by a constant inflow and overflow, so as to cover the drums to the depth of a few inches. Powder thus stored would not only be absolutely free from accidental explosion, but would also defy the incendiary. Any flaw in the drums or defect in the cover, now probably the most frequent cause of explosions, would result merely in spoiling a small quantity of powder, at the same time leading to the immediate detection of the faulty drum. Owing to the hexagonal form of the drums, they would pack closely together, and very little water would be required to cover them, so that the same mode of storage could be used in barges, in floating magazines, or even in war-ships; while the necessary freedom of the drums from any adhering grains of dry powder would render the transmission of powder from the magazines to any other place exceptionally free from danger. Some years ago I sent a detailed statement of this proposed method of water storage to the then Secretary to the Admiralty, Sir Thomas Brassey, requesting him to lay it before the proper authorities. I was informed in reply that it was thought that my method might have some advantages, but that there were certain practical difficulties, and that I had better make myself acquainted with the actual mode of storage; to enable me to do which an official volume on "Ammunition" was sent me. I found by this volume that metal drums, somewhat similar to those proposed by me, were already in use, so that there was no difficulty on this score; but that elaborate rules and directions were in force for the purpose of preventing explosions, which nevertheless still occur. I submit, therefore, that a method which would render all such elaborate precautions unnecessary, and which would entirely remove the alarm each fresh explosion causes to those who are obliged to live in the vicinity of our great powder magazines, is worthy of a careful trial by our military authorities. --I am, Sir, yours obediently,

Alfred R. Wallace.
Parkstone, Dorset.