Question: Which Irish ballad written by Frederic Weatherly was featured on the album The Sweatheart Tree by Johnny Mathis?

Context paragraphs:
The Sweetheart Tree: The Sweetheart Tree is an album by American pop singer Johnny Mathis that was released by Mercury Records on September 30, 1965, and included songs associated with Italy ("Arrivederci Roma"), France ("Clopin Clopant"), Ireland ("Danny Boy"), and Scotland ("The Skye Boat Song") as well as several selections, such as "I'll Close My Eyes" and "The Very Thought of You", from English composers.

The Best of Johnny Mathis 1975–1980: The Best of Johnny Mathis 1975–1980 is a compilation album by American pop singer Johnny Mathis that was released in the fall of 1980 by Columbia Records.  This collection is similar to his last major compilation, 1972's "Johnny Mathis' All-Time Greatest Hits", in that it excludes many of his American radio hits of this period ("Arianne", "Begin the Beguine", "Do Me Wrong, but Do Me", "Loving You-Losing You", "One Day in Your Life", "Stardust", "Yellow Roses on Her Gown", and "You're All I Need to Get By", all of which made the Adult Contemporary chart in "Billboard"

Danny Boy: "Danny Boy" is a ballad set to an ancient Irish melody.  The words were written by English songwriter Frederic Weatherly and usually set to the Irish tune of the "Londonderry Air".  It is most closely associated with Irish communities.

The Classic Christmas Album (Johnny Mathis album): The Classic Christmas Album is a Christmas compilation album by American pop singer Johnny Mathis that was released on October 7, 2014, by Columbia Records and includes two 1961 recordings that were previously unavailable: "Ol' Kris Kringle" and the original version of the title track from his 1969 Christmas album "Give Me Your Love for Christmas".  Three other songs ("Christmas in the City of the Angels", "Sign of the Dove" and "The Very First Christmas Day") make their debut on compact disc as of this release, and two other non-album singles ("Christmas Is..." and "My Kind of Christmas") can be counted among the rarities here.  The collection also includes a selection or two from several of Mathis's Christmas studio albums—"Sleigh Ride" from "Merry Christmas", "Have Yourself a Merry Little Christmas" from "Sounds of Christmas", "Calypso Noel" from "Give Me Your Love for Christmas", "The Christmas Waltz" and "It's Beginning to Look a Lot Like Christmas" from "Christmas Eve with Johnny Mathis", and "Home for the Holidays" from "Sending You a Little Christmas"—as well as his duet with Bette Midler from her 2006 holiday album "Cool Yule", which was a medley of "Winter Wonderland" and "Let It Snow!  Let It Snow!  Let It Snow! ".

The Holy City (song): The Holy City is a religious Victorian ballad dating from 1892, with music by Michael Maybrick writing under the alias Stephen Adams, with lyrics by Frederic Weatherly.

Johnny Mathis: Wonderful, Wonderful!: Johnny Mathis: Wonderful, Wonderful!  is a television concert by American pop singer Johnny Mathis that was recorded on October 27, 2006, at the Tropicana Hotel in Atlantic City and aired that December on most PBS stations.  In addition to singing some of his biggest hits, he covers tracks from his live albums ("In the Morning" from "" and "To the Ends of the Earth" from "Unforgettable – A Musical Tribute to Nat King Cole"), songs from Brazil ("Manhã de Carnaval" from "Olé" and "Brazil (Aquarela do Brasil)" from "The Ultimate Hits Collection"), and two exclusives ("Let Go (Canto de ossanho)" and "Pure Imagination") that have never appeared on a Mathis album.  Interview clips with Mathis were inserted at intervals throughout the concert along with live performance excerpts from programs such as "The Tonight Show Starring Johnny Carson" and "The Andy Williams Show".

Up All Night (The Chic Organization album): Up All Night is a compilation album by Nile Rodgers and The Chic Organization, released in 2013.  It contains recordings written, played and produced by Rodgers and Bernard Edwards for various artists including Sister Sledge, Diana Ross, Sheila & B. Devotion, Deborah Harry, Norma Jean Wright, Carly Simon, Johnny Mathis and their own group CHIC.  In its original form, the album included every UK Top 40 hit single produced by Chic, excepting remixes.  The Johnny Mathis track was widely publicised as being previously unreleased, though it had in fact appeared on Mathis' own "Ultimate Collection" CD in 2011.

Johnny Mathis (album): Johnny Mathis is the debut studio album by vocalist Johnny Mathis that was released by Columbia Records in 1956.  The subtitle "A New Sound in Popular Song" can be found on the back cover but not on the front of the album or the disc label; in fact, this Mathis LP has been referred to as "the jazz album".

The Complete Christmas Collection 1958–2010: The Complete Christmas Collection 1958–2010 is a three-disc box set by American pop singer Johnny Mathis that was released in 2015 by Real Gone Music under license from Columbia Records.  The set includes Mathis's five holiday albums from the period in their entirety: "Merry Christmas", "Sounds of Christmas", "Give Me Your Love for Christmas", "Christmas Eve with Johnny Mathis", and "The Christmas Album".  It also compiles all of Mathis's holiday songs that were only released as singles, as well as thematically-appropriate tracks from his non-holiday albums: "When a Child Is Born" from "I Only Have Eyes for You", the holiday version of "What a Wonderful World" from "Let It Be Me", and his two recordings of "Ave Maria" from "Good Night, Dear Lord", which bookend the set.

In the Still of the Night (album): In the Still of the Night is an album by American pop singer Johnny Mathis that was released in August 1989 by Columbia Records and continues the trend that began with his 1986 collaboration with Henry Mancini, "The Hollywood Musicals", in that the project is devoted to a specific theme that ties the songs together.  Mathis hints at the theme for this album in the liner notes for his 1993 box set "The Music of Johnny Mathis: A Personal Collection", where he gives his thoughts on the 1964 Little Anthony and the Imperials song "I'm on the Outside Looking In" that he covered for his 1988 album "Once in a While": "That was group singers' kind of material.  I was singing other stuff.  It wasn't the picture of the lone crooner standing in the spotlight.  That's what I was doing when all this other stuff was going on.  I never listened to it until it was brought to my attention by [that album's producers] Peter Bunetta and Rick Chudacoff."  Mathis chose to continue his work with Bunetta and Chudacoff on this project, which focuses on "this other stuff" that Mathis refers to: pop and R&B hits from the 1950s and 1960s.

Supporting paragraphs: The Sweetheart Tree Danny Boy
Answer: Danny Boy