Category: Divine Stone

As master builder, James Bambridge’s job is to plan and direct the overall project. He coordinates the production of working drawings from the architect’s plans with the delivery of stone from the quarry. He has to follow the stone’s progress through the yard and its final application to the southwest tower. Ordinarily, a specialist working under Bambridge would do the setting out. They would turn out half-inch scale working drawings from the architect’s one-eighth scale renderings. They would also produce the full scale templates in zinc. These cross sections of complicated stone units, such as colonetted columns, are laid out on a spacious floor. It would be similar to a full-scale lofting floor in a boatyard. Bambridge had space in the cathedral’s crypt for doing this.

The interior was largely complete by the time construction ceased in 1941. The exterior, where the absence of any towers created a harsh, cut-off look was much more obviously unfinished. The original architectural firm of Ralph Adams Cram became Hoyle Doran and Berry Architects in the 1940’s. Cram left drawings for the front two towers, as well as for a still larger Central tower over the cathedral’s crossing. The latest revisions to the cathedral drawings were done by Cram before his death in 1942. It is these drawings that provide the basic outline for the work facing Bambridge and his crew. John Doran of the successor firm was one of only a few architects at the time that construction on the cathedral restarted in the 1980’s that could draw gothic structures.

Starting Where the Architect Left Off

The process is complex, however, since the designs Cram left were never detailed or made into working drawings. Since the size, shape and placement of each stone must be determined in advance, Mr. Bambridge’s role in design was as crucial as the architect’s. While initial preparations were underway in the stoneyard, Bambridge worked on the drawings from his home in Cornwall and in New York. He had an office in Diocesan House and an apartment in Synod House, both in the Cathedral Close.

The working drawing shows every stone in the face. In the center of each is a circled number. Each stone has its own number and each has a card in Bambridge’s file describing it and its position, in code. S would mean the south tower. D means it’s the fourth section up. The fraction numbers are its dimensions. The other number is its cubic volume. At year’s end, Bambridge totes up how much foot cubage is produced. He checks it against the foot-cubage the quarry has delivered and arrives at a waste factor. That factor is important in cost control. His nerve center is a room in the cathedral’s basement. Crouched on the floor, he turned the drawings into programs for stone cutting.

The Setting Out Uses Zinc Templates

Zinc is used in making the templates as it does not contract or expand based on the temperature in the stone cutting shed. It was necessary to create full size drawings of some sections in order to make the trade work templates. This was done by first sliding a sheet of zinc under the full size drawing. Holes were then pricked through the paper at relevant points onto the zinc below along the lines of the drawing creating a series of dots. The dots were then connected to form the lines of the template. The lines were created with a sharp scriber forming a thin groove on the surface of the zinc. The surface was then treated with a copper sulfate solution which reacted with the zinc to make black clear lines. The zinc was then snapped by repeating the scribing process or cut with tin snips.

In addition to cutting the template, the specialist would specify joints for the stonecutters, produce a job ticket on each stone to be cut and take care of production schedules. Since only Bambridge was in on the original planning and timetable decisions, he did both planning and directing. Bambridge later taught D’Ellis Kincannon this part of the process and turned it over to him. He became highly accomplished at the setting out process. Cynie Linton also learned to do the setting out. Over time, mylar replaced the traditional zinc which made an easier and less expensive process.

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From Cutting Shed to Tower

Each card in Bambridge’s file becomes a job ticket that goes to the stoneyard. When a stone is produced from it, the master mason takes a crayon pencil and colors that numbered stone on his copy of the working drawing. This system means that no stone is duplicated. The stones are cut to millimeter accuracy, just like medieval stonework. The towers could be put up dry. Mortar is used to take up minute discrepancies in the stone, and to keep out the weather.

The yardstick used is to design and cut so that it would stay up there on its own with no mortar.

– James Bambridge

In a modern masonry building, once the second floor is designed, the same pattern repeats for the next 20 floors. Here, each stone is an individual piece to fit a given space. In the 12th century they would work the stone as it came from the quarry. The stone was cut to whatever it would make. To keep faith with that medieval system, Bambridge would deliberately throw in an off-length ashlar or quoin. Therefore when someone looks up at the building it would not look totally repetitive all the way up. The eye is forced to move around. This then replicates more of the old Gothic style.

Dean Morton liked to point out that the use of such 700-year-old techniques is what separates the work at St. John from other contemporary cathedral building projects, such as the National Cathedral in Washington, D.C. “Their ashlars are all cut and finished to standard sizes at the quarry. They’re delivered to the site ready to lay up like bricks.”

Thanks to Steve Boyle for all he contributed to this post

The stone mortared into place on September 29, 1982 was the cornerstone of the cathedral’s southwest tower. The date was the feast of St. Michael and All Angels or Michaelmas. It marked 41 years since construction on the cathedral had taken place. The stone cutting apprentices, whose numbers had swelled to about two dozen, had assembled an inventory of cut stone for the last three years. Some 2500 stones had been prepared and now was the time for these first stones to be set. The Very Rev. James P. Morton, dean of St. John the Divine noted that the first cornerstone for the cathedral had been laid in 1892 at the east end. The second, for the nave, was laid in 1925. Each formal cornerstone dedication has marked a significant phase of construction activity.

Cornerstone restarts construction

The cathedral had stopped building during World War II. Work was not resumed because the Episcopal Diocese felt that the erection of a lavish structure would be symbolically inappropriate until the poverty of its upper Manhattan neighborhood could be alleviated. Dean Morton, dean of the cathedral since 1973, realized that perhaps construction itself was the remedy. As a result if community residents were taught to build the cathedral themselves they could gain skills. Likewise this would knit together the cathedral and the community. The apprentices work under the master mason, James Bambridge, who said this of his charges:

All have learned faster than I would have expected – they are really more mature than the younger apprentices I have trained in England, and that makes all the difference.

-James Bambridge

The stone was a gift from Jerusalem Mayor Teddy Kolleck. The Jewish Mayor and the Episcopal Bishop Paul Moore Jr., pledged to exchange limestone blocks for their building projects. First of all the “Jerusalem stone” will be the cornerstone of the southwest tower. The exchange stone, the “St. John the Divine stone”, cut in the stoneyard, will be set among the oldest paving stones of Jerusalem’s Via Dolorosa. This is the traditional path to Calvary, which is in the process of restoration. The ceremony of the stones was held in January, 1981.

The Walk Across Amsterdam Ave

Aerialist Philippe Petit carried a silver trowel across Amsterdam Avenue on a high wire to Bishop Moore, who blessed the stone. Petit and the cathedral were not strangers. This story from The New Yorker: “Philippe Petit has been an artist-in-residence at the cathedral since 1980. He fell in love with the place when James Parks Morton, the cathedral’s charismatic and somewhat unorthodox Dean, invited the fledgling Big Apple Circus, with which Petit had appeared once or twice as a guest artist, to use the Synod House as its circus school for a few weeks. Petit told Morton he would like to do a high-wire walk inside the cathedral.

Morton, who knew about the association of cathedrals and tightrope walking in the Middle Ages, was all for it, but his trustees said no. (What if he fell?) Petit put up a cable anyway and did his walk. When he came down, the police arrested him for trespassing. They were taking him away in handcuffs when Dean Morton, who hadn’t witnessed the walk, appeared and told them to release the culprit. ‘He wasn’t trespassing,’ Morton told the cops. ‘He is an artist of this cathedral.’ Afterward, it seemed like such a good idea that Morton and Petit made it official.”

Part II – The Giant Lathe

To turn the large stone blanks from the granite by the sea into columns required a lathe of unheard of size, because each of the 310 ton raw stone blanks needed to be sculpted to 54 feet high and 6 feet in diameter. As a result the final column would weigh 160 tons. The church commissioned the design and construction of the lathe. It was designed and patented by E. R. Cheney and H. A. Spiller of Boston. It was built by the Philadelphia Roll and Machine Company of Philadelphia. Its construction was begun in December, 1899, and it was delivered at the quarry in May, 1900. It was erected at Vinalhaven under the supervision of J. W. Bourn, the foreman of the machine shop.

The lathe is 86 feet long and weighs 135 tons. It has a capacity to work a stone 60 feet long and a maximum diameter of 6 feet 6 inches. Eight cutting tools are used, each capable of taking up to a 3 inch cut so that the column can be reduced 2 feet each time the cutters traverse the entire length of the bed. In practice the cut was usually set at 1.5 inches. The result is a splintering or spalling of the face of the stone.

Dressing and Polishing the Column

When the column is dressed to shape, cup shaped devices are attached to the tool posts and filled with hardened steel shot. This gives the surface a rough polishing. Likewise, the final high polishing is done the same way using sand and powdered emery. The granite columns make 1.75 revolutions per minute during the operation of turning. During the polishing operation the column makes about 3 revolutions per minute. The countershaft to which the lathe is belted is driven by a steam engine of 50 HP. Finally each 300 ton blank will be reduced to 130 tons and take 6 weeks to complete.

The scientific, architectural, engineering and manufacturing communities followed this mammoth undertaking for months. Therefore the design, quarrying, turning and polishing of the granite by the sea and the lathe captured the attention and imagination of a large portion of the country.

The First Granite Stone Broke in the Lathe

It was found impossible to turn the columns in single blocks. The first three put into the lathe broke under their own weight after considerable work had been expended on them. The ends of the granite columns were held in large chucks or faceplates. Therefore the entire weight of the column was carried by these two faceplates, almost 60 feet apart. As a result therein was the problem as the first stone broke in the middle.

The designer of the lathe said that the proportions were to blame and that the design length would need to have a diameter of eight feet in order to sustain its own weight. It was also indicated that some areas of the quarry had a seam running through it which made it necessary to cut some stone across the grain. Various attempts were made to reduce the bending stress in the middle without success.

Also, numerous other plans were suggested by ingenious inventors to get the granite by the sea on a lathe. One of the most promising was to set the column on end on the center of a revolving table and turn it by tools traveling on a fixed vertical bed. While this plan may have been all right mechanically, the cost of a 75 foot stable tower to support the stone from deflection and carry the turning tools was not practical. The mere setting on end a block of stone weighing some 300 tons was a task not to be taken lightly.

“No Monolithic Columns for the New Cathedral”

In the end, the quarry insisted that monolithic columns would not be possible and the Board of Trustees had no alternative but to accept the new dimensions of a two part column. The lower piece would be thirty-eight feet long and weigh 90 tons. In contrast the upper piece would be 17 feet long and weigh 40 tons. The diameter of the columns would remain at 6 feet.

• Scientific American, January 12, 1901
• Engineering News, December 3, 1903
• Machinery Magazine, April, 1901