On a rainy day more than 20 years ago, educator William Quigley Jr. and his colleagues were hauling archival materials from a flooding basement at the Governor's Academy in Byfield, Mass., when they came upon a mystery.

One of the rescued items - a cardboard box - contained a Civil War-period scrapbook of letters from a Union soldier to his father, the rector of Philadelphia's Christ Church.

The letters in flowing cursive were accompanied by pressed wildflowers and sprigs of shrubs collected at camp sites; blue and red felt military insignia disks, and pencil and ink drawings depicting military life.

The find intrigued Quigley. What happened to the son - and his father, who so treasured the letters that he kept a scrapbook?

Head of the history department at the preparatory school, he located letters and sermons from the rector that portrayed two wars: one fought by the soldier, another by the rector in Philadelphia.

Far from the deadly battlefields that Capt. William White Dorr knew, a conflict raged within the Rev. Benjamin Dorr's Christ Church.

"This remarkable, atypical story was nearly lost to history," said Quigley, whose research has resulted in a book, Pure Heart - The Faith of a Father and Son in the War for a More Perfect Union, to be launched during a free public event at 2 p.m. Saturday at Christ Church, on Second Street above Market Street.

While his son led troops, the rector led a fractious congregation and found himself cast in a Lincoln-like role, trying to hold together a flock that included the city's leading antislavery, pro-Union Republicans and pro-Southern, anti-emancipation Democrats.

The congregants "were Philadelphia's elite, but they weren't people normally associated with histories of the Civil War," said Quigley, 60. "In Benjamin and William Dorr, we see the spirit of civil union as opposed to civil war."

Their letters offer a fresh look at the conflict - with a Philadelphia perspective, local historians say.

They "fill a gap in our knowledge of the city," said Neil Ronk, senior guide and historian for the Christ Church Preservation Trust. "The Civil War divided Philadelphia, in a sense, far more than the Revolution."

The "poignant correspondence reveals the close relationship between father and son, and provides a fascinating inside view to the political divisions and conflicts on the home front and the son's gritty war front experiences," added Andy Waskie, a Temple University professor, Civil War historian, and author of Philadelphia in the Civil War - Arsenal of the Union.

The 24-year-old William Dorr was going to practice law in Philadelphia, but as Union morale sank in the summer of 1862, he enlisted and served as an officer in the 121st Pennsylvania Volunteers.

His duty took him to some of the war's epic battles: Fredericksburg, Chancellorsville, Gettysburg, the Wilderness, and Spotsylvania Court House.

During that time he wrote nearly 200 letters, Quigley said. Twenty were found in the scrapbook.

Dorr described rainy nights on picket duty, camp life, including religious services, and reported on soldiers in his regiment that his father knew.

Then came the fighting at Fredericksburg, Va. The battle was a costly disaster for the Union but Dorr's unit performed well.

In Philadelphia, meanwhile, the elder Dorr's church had become the center of contentious political division in Pennsylvania, said Quigley. Some members, such as former Philadelphia Mayor Peter McCall, exulted over Southern victories.

Intellectual disagreements turned to personal animosity. Because of his views, McCall resigned or was dismissed from his position as the church's principal lay leader in early 1863 and left the congregation, Quigley said.

At the same time, Christ Church also had Union loyalists, including founding members of the fledgling Union League, formed to support the Union and Lincoln's policies, Quigley said.

From the other war came regular reports from William Dorr: "The men suffered severely from the fatigue of long and heavy marches" after the Battle of Chancellorsville, and "they were not in the best condition . . . The heavens sent torrents, and earth, yes, that sacred soil of Virginia, condescended to liquify to a degree and stick to invading Yankees that they might thereby be overcome and destroyed."

Months later at Gettysburg, Dorr and his regiment were yards away from the climactic end of Pickett's Charge and witnessed hand-to-hand fighting. The grim toll shook him.

"We started this morning . . . marching over the battlefield, a thing I don't care to do again if to be avoided," he wrote his father. "It will be found that the loss of both sides has been enormous."

On May 7 in Philadelphia, while his son prepared to descend deeper into the Wilderness in Virginia, Dorr penned an anxious letter, Quigley said. "As usual, we have all sorts of rumors afloat, as to the objects and progress of the movements thus far, but nothing yet very definite or reliable," the father said. "I need not say how anxiously we shall wait and watch for the coming news."

He then wrote his last words to his son: "Everybody seems hopeful that the present campaign, by God's blessing, will bring this terrible rebellion to an end." He closed with a prayer: "May our Heavenly Father have you in his special keeping, and 'bring you out of all perils, to show forth his praises forever,' is the constant prayer of Your affectionate father, B. Dorr."

Capt. Dorr's last letter to his father, written May 8 and 9, described his regiment's movements and contact with the enemy, then noted with satisfaction, "No colors lost."

The soldier was killed May 10 leading the 121st Pennsylvania in an attack on the fortified rebel line atop Laurel Hill outside Spotsylvania Court House, Va.

A comrade, Lt. Henry H. Herpst, wrote to one of Dorr's sisters describing a conversation hours earlier. Dorr "said to me, Harry I wish this campaign was over," Herpst wrote. "Not that I fear it but I know it will be bloody. He then said I may fall but I shall do my duty as a soldier and put my trust in God."

Herpst was near Dorr when he was shot in the heart. "He had just rallied the regt. and was in the front line close by the colors," he wrote. "When he fell, I sprang to his side raised his head and listened to catch any word he might utter. But he never spoke. He suffered no pain as he was dead instantly."

The history of the soldier and the rector "hold lessons for our times," Quigley said. "Both spoke a language that is more civil and compromising. They were not self-righteous but had a spirit of humility and charity."

Three memorials, to Benjamin Dorr, his wife, Esther, and their son were erected at Christ Church. The one to William Dorr "will serve to perpetuate the memory of a gallant soldier and noble Christian gentleman," the Inquirer reported in 1865, "and it is well placed in a church where his name will always be held dear."

Edward Colimore is a former Inquirer reporter who has written extensively about the Civil War and the history of Philadelphia. ecolimore@comcast.net