October 20, 1916. THE COLLIERY GUARDIAN. 747 operated bridge transporters, which span the width of the storage ground, and travel the whole length of that ground, on tracks on either side. These bridges are supported on wheel bases or trucks, and they have two transport tracks, the lower being for storage transfer cars, whilst the upper track carries two movable jib cranes, each of which operates with a grab of five tons capacity, and serves to take from storage. The cranes are provided with electric winches having differential gear so arranged that the grab takes a definite course inwards and outwards during its vertical travel between the storage pile and the bridge hopper. On an inter- mediate track just below that of the jib cranes two movable hopper chutes are provided, which are used in conjunction with the cranes, and take the discharge from the grabs for delivery to the transfer cars on the track beneath; these transfer cars thus serve also for * w/ * I J * I »;/ / J Fig. 2.—Coaling Afloat with Portable Elevators. is also supplied by the transfer cars. Transfer of coal can, of course, be effected to keep pace with the rate of the discharging cranes. The grab track of these dis- charging cranes is 180 ft. in length, the overside end being 75 ft. in length, and hinged so that it can be raised out of the way of the vessel’s rigging when not in use. For taking from storage, the two transporter bridges have a combined capacity of 2,000 tons per hour, and storage can also be turned over to different parts of the ground by means of the transfer cars traversing one or other of the storage bridge tracks. The transfer cars, when loading the elevated bin at the end of the pier, discharge into a hopper which serves conveyors. The weight of the coal dealt with is ascertained by track scales on the elevated trestle, and the system of weigh- ing is intended to be duplicated and checked by auto- matic record. Other track scales are available for the this question will be referred to further later. The United States Government, with the object of facili- tating supplies of coal from the States, and ensuring regular deliveries and minimum costs of transport, has provided two special coal-carrying vessels, each of which has a cargo capacity of 12,000 tons and a speed of 13 to 14 knots." These colliers will also be operated by the Panama Railroad Company, who have made an offer to run the vessels 17 voyages per annum, and to carry 210,000 tons of coal at a cost of 97c. per ton. Conditions as to Coal Supplies. Before proceeding (in the next article) to the arrange- ments and equipment at Balboa—the Pacific terminal—■ it may be well to refer briefly to the conditions relating to coal supplies at both terminals. The tolls and rates are so arranged that the Panama Railroad shall not com- pete with the canal, and that it will not be possible to transport coal by railroad across the isthmus at a lower cost, the United States Government also having con- trol of the railroad, as already indicated Coal discharged at the canal terminals for supplies to shipping will not be liable to duty, although pilot and wharf charges are to be made. Vessels receiving coal supplies, how- ever, will not be subject to these charges. The rental to be charged to coaling contractors for a lease of storage ground is 20c. per sq. ft. per annum, which provides for approximately half a ton. Allowing the coal to be in store for, say, an average of two months, the storage cost will amount to about 6Jc. per ton sold. Coal will only be discharged from single deck vessels, and the canal authorities may prohibit the storage of coal con- sidered by them to be of an unsatisfactory quality. This latter appears to be a rather questionable condition, as it is difficult to define and decide whether coal is to be considered unsatisfactory from the point of view of liability to spontaneous combustion and damage to adjoining coal, the equipment or wharf, or whether as being inferior for ship’s use. As to charges and despatch, 25c. per ton is to be the rate for discharging coal cargoes, including trimming and stacking where required on the storage ground, for taking from any part of the storage including trimming at the stack, and delivery to vessel alongside the wharf but not including trimming in the vessel’s bunkers, the charge will be 20c. per ton. Vessels will be guaranteed wharfage accom- modation for discharging coal cargoes within 24 hours of the time of arrival, and the rate of discharging to storage will be guaranteed to be 1,000 tons per day of 24 hours; despatch money of 8c. will be charged, and demurrage of 4e. allowed, based on the net registered tonnage of the vessel. The maximum price which may be charged by suppliers will be fixed by the railroad company, and it may be mentioned that the maximum stated is 25 per cent, above cost, the lessees being required to furnish the necessary information to enable the cost to be re-handling from storage. The loading equipment com- prises four movable plants of special design, also elec- trically-operated. They are supported on gantry frames and travel on two rail tracks, 26 ft’, from centre to centre, along the deep water part of the loading wharf. These loading plants include a tower frame with a hinged jib truss, which carries a belt conveyor; and at the outer or discharge end of this jib is suspended a hopper with a telescopic adjustable chute. Each of these plants can handle up to 600 tons per hour. These loaders are served by a portable conveyor and hopper supported on a wheel base frame, which travels on a track parallel with and adjoining the re-loader track. Around the whole storage ground is a steel trestle structure, which supports a double rail track of 3 ft. gauge at an elevation of 29 ft. above the wharf decking. This provides for the coal transfer cars, and includes about 1,200 ft. of storage track at the shore end of the pier. The transfer cars are of steel construction, of the saddle or double hopper type; they have a capacity of 10 tons each, and travel at a speed of 200 ft. a minute by means of electric motors. The end wharf is provided with an elevated bin of rein- forced concrete construction, having a capacity of 1,500 tons. This bin is about 100 ft. in length, and is divided into three sections, which are designed to be self-dis- charging through adjustable and telescopic chutes. Both the loading and discharging sides of the pier are served by 5 ft. gauge railway tracks connecting with the Panama Railroad. One of these tracks passes under the tower gantries of the loading plants, and another track passes under the gantries of the discharging cranes, whilst the storage transporter bridge tracks are also used for the railroad service. System of Coal Handling. Having briefly outlined the design of the Cristobal coaling station and the equipment provided, it may now be of interest to refer to the system of operation. The discharging cranes will discharge colliers into the transfer cars on the elevated tracks, the starting, stopping, and discharge of these cars being controlled from a platform between the two tracks. The cars travel over the required route, and discharge automatic- ally at the position desired. In the ease of discharging and loading direct, the ears on the inner track will dump into a hopper chute suspended beneath the track, and movable to the required position along the loading wharf. This chute will serve the portable hopper and conveyor, and the coal is transferred by this to the loading con- veyor. The car on the outer elevated track will dis- charge direct into the portable hopper chute. The loading of the ears is effected from a hopper on the discharging tower cranes served by the grab through the main hopper and short conveyor, whilst the main hopper also serves the railway track beneath by means of chutes. In the case of storage, the transfer care are switched on to the tracks of the transporter bridges, and these tracks can also be used when required, and when advantageous to serve the loaders. The elevated bin at the end wharf J? . A"*' , f MBS"*” ~ ■ i •-•cjV Fig. 4.—Coal Storage Ground, Cristobal. (Showing Basin for Storage under Water.) railroad at the wharf level, for checking delivery to rail- way wagons. Finally, it may be added that a com- munication signalling system is provided, both sight and sound methods being adopted; and the electricity for working the whole equipment (with the exception of the discharging cranes, which are steam-operated) is obtained from the canal power house, the three-phase high-pressure supply being transformed to a lower voltage at a sub-station. It will be observed that the equipments provide for handling extensive quantities of coal, ■which the authorities anticipate will be required when the use of the canal becomes general; and the figure of 1,000,000 tons per annum is mentioned as likely to be reached in a few years. It is realised, however, that the patronage secured for the canal coaling stations will greatly depend upon the cost of the coal supplies; and proved; and, in addition, it should be noted that licensees may be required to supply from their storage any vessel passing through the canal. (To be continued.) Grimsby Coal Exports.—Last week’s exports of coal from Grimsby totalled 8,312 tons foreign and 930 tons coastwise, against 16,781 tons foreign during the corresponding period of last year. Institution of Civil Engineers.—A special meeting of the institution will be held at Great George-street, Westminster, on Tuesday, October 24, commencing at 5.30 p.m. Sir J. P. Griffith will deliver the 24th James Forrest lecture on “ The Development of Appliances for Handling Raw Materials and Merchandise at Ports and other Large Centres of Traffic.”