largeness of the windows, which frame, as though they enclosed pictures, beautiful views in almost every direction, thanks to the location of the building. The interior finish in hard woods is excellent, and is matched by the best quality of plumbing, tiling, etc. Starting at the sub-basement of this massive building, we find there the engine and boiler rooms, the pump room, coal vaults, the dynamo room, the motor-generator room, etc. Each of these important departments will be described in detail, later, when it will be seen that the Postal Building is the latest and finest exemplification of a very wide range of the modern electrical arts. Above the sub-basement, itself 12 feet high, is a lofty basement which is to serve the Postal Telegraph Co. as supply and storage From the second up to the tenth floor, inclusive, the space will be occupied by private firms, etc., and the offices already taken house a good many electrical concerns, such as the Sprague Electric Elevator Co., Walker Mfg. Co., Dr. C. T. Hutchinson, P. Lemaire, W. J. Johnston Co., Ltd., etc. etc. The eleventh floor the Postal Company has reserved for its own executive offices and accounting departments, in the rear half, while the front half has been taken by the Commercial Cable Co.; Mr. Mackay having a private office midway between the two. This is practically an executive floor, and it is most conveniently arranged for the swift transaction of business. Above it comes the general operating department which occupies a superb, high pitched hall, Fig. 1, that covers the entire twelfth floor. It has light FIG. 1.-MAIN OPERATING ROOM ON THE 12TH FLOOR, POSTAL TELEGRAPH BUILDING. department, linemen's and messengers' rooms, and is therefore equipped with every facility for the disposal and distribution of supplies. The first floor at the street level is a magnificent receiving and delivery department for the company's local traffic. It is lined with rich yellow Sienna marble, trimmed and finished with solid brass mountings, rails, etc., and paved with mosaic. The public gains access to this chamber, from the outside, through a lofty alcoved entrance, above whose entablature are two graceful figures expressive of the character of the building; while on each side of the wide portal are mounted huge ornamental flambeaux, each sixteen feet long, surmounted by a Commercial Cable globe masking a cluster of incandescent lamps. The effect is quite grandiose and impressive. from four sides, and its windows are very large, the ceiling being 18 foot pitch. The thirteenth floor provides room for the miscellaneous staff, and is also cut up into coat rooms, lavatories, etc., arranged with a keen eye to the ease and comfort of the employés. The fourteenth floor has been eagerly preempted by the Hardware Club as a home for its members, who are very thick in this neighborhood, and who can reach their cosy parlors by six rapid electric elevators. This brief statement will give a broad idea of the building and its general arrangement, but we hasten on to discuss a number of the interesting and novel features which make the new Postal so striking an exhibition of all that is most modern and successful in electrical engineering development. The officers of the Company have in this FIG. 2.-THE POSTAL TELEGRAPH DYNAMOTOR PLANT AND DYNAMO TELEGRAPH BOARD. employed exclusively for the local work, such as sounders, etc., and the other machines give all the range and flexibility required for the system. of consideration and the question merely resolved itself volts + or -; one 130 volts + or -; one 200 volts + or into devising the most simple and reliable system of cur--; and one 350 volts + or. The 40 volt machine is rent generation for telegraphic purposes. As a result of a thorough study by Mr. Francis W. Jones, chief electrician of the company, of the conditions, it was resolved to employ motor generators or dynamotors, in preference to machines driven by belting from shafts. By employing dynamotors each machine is entirely independent of every other and, as we shall see presently, the number of relay machines required is only one-half that which would be necessary, where all the machines are dependent upon a single out side source of power. The selection was also made possible by the fact that two main independent sources of current supply were available, namely that of the building itself and that of the Edison Electric Illuminating Co., whose circuits have been connected to the building, and, in fact, have been wholly depended upon until the completion of the building's steam plant. The machines, sixteen in number, built specially by the The maximum output of all these machines is 11,950 watts and they are calculated to replace 47,725 cells of Callaud battery. Aside from the enormous saving in space as well as in economy of operation, the low resistance of the dynamo generators, as compared with that of the cells, materially improves the service, especially in wet weather, when "cross fire" has in the past created much annoyance on continuous lines. This will be obvious when we consider that with two or three lines connected to a single battery of high resistance, part of the current coming in on one line is apt to branch off into another line connected to the same battery. With the dynamo offering but a few ohms resistance, even at the highest potential employed, the resistance to ground is practically nil as compared with that of the line, and hence any number of wires might, in practice, be connected to the same current source without causing disturbance from "cross fire," due to the cause mentioned. Fig. 3 shows the dynamotor in perspective. Besides being very finely finished, and made to comply FIG. 3.-CROCKER-WHEELER TELEGRAPH DYNAMOTOR. in every detail with the particular requirements of the Postal company, these machines have some special features. They are provided with regulators having 43 contacts giving 40 steps of regulation, each carefully calculated and arranged in a logarithmic proportion, so that with any load on machines from lightest to full load, the effect of turning the regulator one step, whether near the "full on," or the "full off" position, changes the E. M. F. of the machine the same percentage. That is, the action of the regulators is absolutely uniform in all positions and at all loads, and their capacities are such as to reduce the E. M. F. 25 per cent. below the maximum, even when the machine is running empty. No margin is allowed for raising the voltage above normal, but the machines are all built for normal voltage a little in excess of that required. Every machine is severely tested for the very highest insulation. The oiling arrangements and the position of machines are such that they will run a month at a time with absolutely no attention of any kind, and will run a year or more with no attention but renewal of oil. IV. THE TELEGRAPH DYNAMO BOARD. Situated close to the dynamos is the telegraph dynamo board which forms the connecting link between the machines and the operating room on the 12th floor of the building. It is to this board, Fig. 2, that the leads, from the machines are carried and connected to contact-plates controlled by switches which close the circuits to the operating room. The functions of this switchboard will be readily understood from an inspection of the diagram, Fig. 4, which also shows the connections of the machines to the main switchboard. For simplicity's sake, we have shown the machines of but one potential connected to the board, namely that of 350 volts. Two of these machines, A and B, are always in regular operation, furnishing the plus and minus potential, with a third as a relay, which can be thrown in to replace one of the others when necessary, as will be shown presently. From the brush of machine a the circuit goes first through a fuse and then into a contact plate of the knife switch K'; the + potential of machine B goes to a similar switch on the other side, K. Alongside of each of these switches is another, K', K', from which connections. lead to the relay machine c, while the other side is joined to the same wire as K1, leading to the operating room. The wires from the switches K', K, run to the main switchboard and connect to a reversing switch R S. It will now be seen that when the switch is thrown upward the potential of the relay machine c, is led to the the switch K at the 350+ potential side of the board, and the other terminal of the machine is put to earth; but when the switch is thrown over to the other side the potential is carried to the switch of K connecting with the - 350 volts potential on the board. Normally, of course, the reversing switch is open. It will thus be seen that by merely throwing the reversing switch, R s, the single relay machine can be connected either to the plus or the minus side of the circuit, and its substitution for a running machine is effected without the slightest discontinuity of the working current. The switches s1 s2 s3 which are mounted on the main switchboard controlling the power and lighting circuits of the building, control the motor side of the dynamotors through the starting boxes. All switches on the dynamo board are drilled for the insertion of plugs. Mounted on the board is one of the Weston illuminated dial voltmeters, reading up to 500 volts; by inserting plugs in the drilled contact plates, above referred to, their potential can be read off on the voltmeter and in this way the working of the machines can be checked at all times; at the same time, its use is essential, in order to bring a machine up to proper potential before throwing it into a working circuit. By inserting another set of plugs the strength of the current can also be situated the resistances to protect the circuits fed by the After passing through the board the wires are connected V. THE UNDERGROUND CABLE ROOM. The line wires enter the basement from the subways in wires each, which are carried directly to the cable room in FIG. 5.-PLAN OF OPERATING ROOM, 12TH FLOOR, SHOWING ARRANGEMENT OF TABLES, PNEUMATIC SYSTEM, ETC., POSTAL TELEGRAPH BUILDING. these cables and this has been accomplished in the following way: At the top of the well a heavy steel bar is supported horizontally, to which are fastened inch galvan FIG. 6.-RESISTANCE COILS, MAIN SWITCHBOARD. ized iron stranded ropes, corresponding in number to the number of cables and which extend down to the cable room. At each floor the cables are bound to the wire ropes by marline tow closely wrapped around both. Be sary, the cables can be examined at practically every foot of their run. In addition to the cable room devoted to the purposes of the Postal Telegraph Co., another similar room has been specially provided for the accommodation of telephone, messenger, ticker, and other similar service. The wires of these companies are also brought in by separate conduits from the street, thus leaving the company's service entirely distinct and separate. VI. THE OPERATING ROOM. To those who are accustomed to link the idea of a telegraph operating room with any space capable of holding tables and chairs, the superb operating room on the 12th floor of the building will be a revelation. It extends the entire length of the building-156 feet and crosses the whole front of the building, 70 feet, facing on Broadway, overlooking City Hall Square on one side and the Hudson River and New York Harbor on the west. The ceiling is 18 feet high as already stated; and, with the large windows provided, the light is practically equivalent to that outdoors. The floor space is laid out in standard octet tables made of cherry, which wood is also used for all the switchboards. Situated in the centre of the room is the main switchboard and directly in front of it are the tables containing the repeater sets. Directly opposite these, near the wall, is the manager's table, raised on a platform so that he can readily overlook the entire floor. Near the Broadway wall is the city switchboard. See Figs. 1 and 5. VII. THE MAIN TELEGRAPH SWITCHBOARD. Let us now return to the cables entering the operating room at the back of the main switchboard. Taking first FIG. 7.-MAIN SWITCHBOARD IN POSTAL TELEGRAPH OPERATING ROOM, FRONT VIEW. ing thus supported at each floor, as it were, the cables reach the top without any strain on them whatever and are taken under the floor to the back of the switchboard. The cable well is accessible at each floor, so that, if neces the 14-wire dynamo cables, they are led to a small distributing board, at the back of the main board, and thence under the floor to the main switchboard, one to each panel of the board. They are there connected to a common ter |