The "Bone Finder" uses ground-penetrating radar to find lost graves at Congressional For the past several months, Perry has painstakingly paced the grounds of Washington's Historic Congressional Cemetery, tucked in a far corner of the city at 1801 E St. SE, near the Anacostia River. More than halfway done with the search, the grave whisperer has already found an estimated 2,750 unmarked burials. Congressional was founded in 1807 and served as an eternal home for some of America's first congressmen, but its recent history has been one of rebirth after a period of neglect. Perry's work will allow the historic graveyard to enter the modern era and reconcile its records, which Perry ranks among the best he's encountered, with reality. Congressional is one of 12 cemeteries in the District still accepting new residents alongside people such as Civil War photographer Mathew Brady. But choosing a site for a new burial isn't always a sure bet. Over time, headstones go missing and records disappear. The cemetery hasn't had a comprehensive map made of its holdings since 1935. Using carefully calibrated radar, Perry is able to find open space for the cemetery as well as provide a more detailed picture of the bodies buried there. The cemetery's now-pastoral grounds were filled with trash and spent syringes in the late-20th century. In the 1990s, a band of dog walkers raised money to begin a needed clean-up. They envisioned a place open to the public, recalling the Victorian tradition of garden cemeteries, which were often the only open green spaces available to city dwellers. Not everyone embraced the idea of a graveyard full of puppies and joggers, but the group became responsible co-stewards of the site. Every year, the cemetery throws a birthday party for one of its most famous residents, John Philip Sousa, complete with the United States Marine Band. When goats were called in to help manage (i.e., eat) an invasion of poison ivy in August, the quirky cemetery drew eyes from across the country. Margaret Puglisi, vice president of the Association for the Preservation of the Historic Congressional Cemetery, which manages the site, launched the D.C. Metro chapter of the Association for Gravestone Studies at the cemetery's chapel in early November. Perry, 66, a Bostonian who now lives in New Hampshire, at first declined an offer to make a subterranean survey of Congressional. It is much bigger than the hundreds of cemeteries and church plots he has surveyed, many up and down the East Coast. But the staff was persistent, and Perry relented. Now, he says, Congressional is his favorite cemetery. He has to remind himself to focus while he walks the radar up and down the rows because he often gets distracted reading the headstones. Perry talks with a strong Boston accent and has a soft spot in his heart for fellow veterans. He likes the solitary nature of the work he does, the quiet as he walks the grassy streets of a silent city. He's gruff but patient with passersby who stop to ask him about his work. On the job, he wears faded blue jeans, belted, with a tucked-in Oxford shirt. Perry starts every job the same way. He finds a group of graves that have a well-documented provenance. Then he rolls his radar over the plots, slowly, step by step, back and forth. A screen between the cart's handlebars provides a picture of gray squiggles that indicate any sort of anomaly in the ground. Most burials appear as little arches, but other items can show up, too; buried pipes, tree roots and the like. He divides the cemetery into sections and ropes off each one to guide his path. Anywhere he finds an anomaly, he sticks a small red flag in the ground. He has a six-step process for verifying if a gray blip on his screen is a "high-probability burial," as he calls it, or just an errant pipe. When he finds a bunch of blips evenly spaced, side by side, he can be pretty sure those are burials. After serving in the Navy during the Vietnam War and working at various jobs after leaving the military, Perry was asked by a friend who managed a cemetery to help map it. Perry agreed and found that he enjoyed the work. He knew he had found his calling on his first real assignment outside of Boston. It was the opening game of the Red Sox baseball season and, in a patriotic display, jets flew over the city. "Here I am working in a cemetery, it's nice and quiet," Perry remembered. Suddenly, the jets flew by right as Perry was charting a section of veterans graves. "It kind of overwhelmed me completely," he said. It brought a tear to my eye thinking about it, and it's when I felt I finally found the business I should be in. Ground-penetrating radar was first put to use in the Vietnam War. Perry remembers seeing it even though he didn't realize what it was at the time. Perry worked on river patrol boats, sometimes carrying elite forces up and down the waterways. One day, after dropping a crew off, he stopped at an outpost to get something to eat. I happened to see these guys on the ground pulling this piece of equipment around, and it never dawned on me what it was. Years later, he realized that they were searching for enemy cells using the same technology he now uses. Perry comes to Congressional from his home in New Hampshire for a week every month. He can cover an acre in roughly two days, but his pace slows in the swampy summer heat. Of the 16 sections he has surveyed so far, he says he's averaging between 200 and 250 unmarked graves. He's also found pipes that the cemetery didn't know were there. Working in Washington presents some unique challenges. Everything from sirens to radio signals can upset readings. "I can't go five or 10 feet without having to reset the radar," he said. Because you're right there in D.C. - you get all sorts of this stuff in the air. From November to April, Perry takes a break from projects in colder areas, preferring the warmer climes of the Virgin Islands or Hawaii. But he'll be back in the spring to finish the job at Congressional. When he's done, his work will be digitized so users can search the cemetery with a smartphone app. He suspects that most of the unmarked graves he has found will be accounted for in the cemetery's records. But some could be completely new discoveries.