This idea of interspacing filled in with non-combustible material has been generally followed ever since. The particular inventions in that line consist in the discovery and appliance of new lining materials, variations in the form of the interspacing, and new methods in the construction of the casings, and the selection of the best metals for such construction.
In 1834 William Marr of England patented a lining for a double metallic chest, filled with non-combustible materials such as mica, or talc clay, lime, and graphite. Asbestos commenced to be used about the same time.
The great fire in New York City in 1835, destroying hundreds of millions of dollars’ worth of property of every description, gave a great impetus to the invention of fire-proof safes in America.
B. G. Wilder there patented in 1843 his celebrated safe, now extensively used throughout the world. It consisted of a double box of wrought-iron plates strengthened at the edges with bar iron, with a bar across the middle; and as a filling for the interspaces he used hydrated gypsum, hydraulic cement, plaster of paris, steatite, alum, and the dried residuum of soda water.
Herring was another American who invented celebrated safes, made with a boiler-iron exterior, a hardened steel inner safe, with the interior filled with a casting of franklinite around rods of soft steel. Thus the earth, air and water were ransacked for lining materials, in some cases more for the purpose of obtaining a patent than to accomplish any real advance in the art. Water itself was introduced as a lining, made to flow through the safes, sometimes from the city mains, and so retained that when the temperature in case of fire reached 212° F. it became steam; and an arrangement for introducing steam in place of water was contrived. Among other lining materials found suitable were soapstone, alumina, ammonia, copperas, starch, Epsom salts, and gypsum, paper, pulp, and alum, and a mixture of various other materials.
After safes were produced that would come out of fiery furnaces where they had been buried for days without even the smell of fire or smoke upon their contents, inventors commenced to direct their attention to burglar-proof safes.
Chubb, in 1835, patented a process of rendering wooden safes burglar proof by lining them with steel, or case-hardened iron plate. Newton in 1853 produced one made of an outer shell of cast iron, an interior network of wrought iron rods, and fluid iron poured between these, so that a compound mass was formed of different degrees of resistance to turn aside the burglar’s tools. Chubb again, in 1857, and in subsequent years, and Chartwood, Glocker, and Thompson and Tann and others in England invented new forms to prevent the insertion of wedges and the drilling by tools. Hall and Marvin of the United States also invented safes for the same purpose. Hall had thick steel plates dovetailed together; and angle irons tenoned at the corners. Marvin’s safe was globeshaped, to present no salient points for the action of tools, made of chrome steel, mounted in this shape on a platform, or enclosed in a fire-proof safe. Herring also invented a safe in which he hinged and grooved the doors with double casings, and which he hung with a lever-hinge, provided the doors with separate locks and packed all the joints with rubber to prevent the operation of the air pump—which had become a dangerous device of burglars with which to introduce explosives to blow open the doors.
Still later and more elaborate means have been used to frustrate the burglars. Electricity has been converted into an automatic warder to guard the castle and the safe and to give an alarm to convenient stations when the locks or doors are meddled with and the proper manipulation not used. Express safes for railroad cars have been made of parts telescoped or crowded together by hydraulic power, requiring heavy machinery for locking and unlocking, and this machinery is located in machine shops along the route and not accessible to burglars.
About 1815 inventors commenced to produce devices to show with certainty if a lock had been tampered with. The keyhole was closed by a revolving metallic curtain, and paper was secured over the keyhole. As a further means of detection photographs of some irregular object are made, one of which is placed over the keyhole and the other is retained. This prevents the substitution of one piece of paper for another piece without detection. A large number of patents have been taken out on glass coverings for locks which have to be broken before the lock can be turned. These are called seal locks.
Locks of various kinds, consisting at least of the two general features of a bolt and a key to move the bolt, have existed from very ancient days. The Egyptians, the Hebrews and the Chinese, and Oriental nations generally had locks and keys of ponderous size. Isaiah speaks of the key of the house of David; and Homer writes sonorously of the lock in the house of Penelope with its brazen key, the respondent wards, the flying bars and valves which,